Below you will find basic information on buying and caring for your tray and it's accessories.
Buying a Tray
You can use pretty much any tray but it should be a heavier weight and generally a medium to large diameter. You can find trays in silver-tone, gold-tone, or brass and occasionally mixed colorings. Trays can be decorative with designs etched into them or plain. You should look for trays that have a raised edge or lip so that if your contents go sliding the edge can at least slow them down if not stop them from falling off. For full effect you probably want to look into an actual Moroccan tray. You can find suitable trays that are similar at most Middle Eastern grocers if you have one nearby and sometimes they actually have the Moroccan ones too. Thrift stores are a good place to check for trays as well as after holiday shopping (all the fancy serving trays that didn't sell often get reduced to 50% or more). If you can try to balance it on your head to get a feel for the weight. When your buying a decorative Moroccan tray your looking at a price range of $50 - $300 depending on size, material, and intricacy of the design. Non-Moroccan tray that work can be found as low as $10 and up to $100. Moroccan trays sold outside of Morocco are generally priced higher as an "exotic imported" luxury good so you can expect them to cost more. Asian markets often have a variety of trays that are relatively cheap but they usually are either fairly plain or very lightweight. However their more decorative ones usually come in mixed tones and gold-tones which can have a very nice look. The easiest tray to balance will be perfectly circular because it provides more even distribution of weight all around you. Rectangular trays will be harder to balance and generally are too small to hold much on them so it's better to avoid them and opt for a larger tray. Sometimes you can find trays that are more octagonal which can look interesting and balance almost the same as a round tray but you have to watch the edges as they can hurt if you bump your arms into the tray while dancing or if you drop it. You also have to watch out for corners catching on your costume which can cause a snag or rip. If you choose one that has corners you should check the edges to make sure they are not too sharp or pointy. You may want to sand or grind the edges down to make them a little more curved. Like anything you can find tons of results on-line as well. Try using the key words "Moroccan" or "morocco" and "tray." There are quite a few Moroccan importers and on-line shops that carry a variety of trays and other Moroccan goods.
Buying Accessories For Your Tray
If your going for traditional seneeya you'll probably want to buy a Moroccan tea set. This would include a pot and at least six glasses. Moroccan tea pots can be highly decorative and are often metal with designs stamped or engraved on them. The tea glasses are often colorful and usually come in mixed color sets. The most common colors will be jewel tones of red, blue, and green. However white is another popular color. Although less common, you can sometimes find them in other colors such as pale tones, pinks, and purples. There are a variety of styles but the two most common is a clear cup with a thick band of color around the top half of the glass and accented by gold and another where the color is deeper on the top and bottom and fades towards the middle to a pale color or mixes to a secondary color and is often accented with gold in swirls throughout the cup. the second type is a more modern style while the first is more traditional. You can find sets of 6 in one color as well instead of mixed color sets. These types of tea sets are sometimes available at Arab grocery stores but usually only if the owner is Moroccan or if there is a large Moroccan population or high demand for this type of glass locally. Otherwise they will tend to carry the standard China made tea sets. More likely you will need to buy them from a Moroccan Import shop. If you have a physical one nearby you can probably find better deals and get the chance to see the sets in person before buying but otherwise you can find them at on-line stores. When there are sales you can sometimes get sets of six cups for about $8 but more often than not they will cost somewhere between $12 and $24. If you can't get hold of the actual glasses or want something cheaper you can look for smaller candle cups at craft or party supplies which often come in multiple colors. Or you can purchase clear cups and paint the inside with an acrylic or glass paint to give it color. If you want to be truly authentic and serve tea from the pot you'll want some Gun Powder Green Tea and some fresh Mint... by some I mean LOTS. If your looking to do a more modern interpretation of seneeya with lit candles you can use a decorative teapot in the middle or you can find something else pretty to place in the middle (try to make it something with a little weight to it though). you can use traditional tea glasses like those already described or any smaller candle holder. For the candles you'll want a smokeless, preferably dripless (less mess) candle. You can buy long candles and cut them or find short candles. Tea lights could also be used. If there is concern about actual fire (some venues simply won't allow actual flames) you can use LED tea lights with a flicker flame which provides a slightly more realistic flame look. When using actual candles you'll want to melt some wax into the bottom of the cup/candle holder and push the candle down into the soft melted wax before it hardens. This will affix the candle in place and keep it from tipping or sliding around. Ideally the candle should be no taller than the rim of the glass or holder. If you are using LED candles you can place a little tape or putty on the underside and stick it to the inside of the cup/holder. LED candles can be found in a variety of retail stores, candle shops, home decor stores, and of course on-line and will range anywhere from 50 cents for a tealight to $20 for a high quality taper so shop around for "LED candles" "battery candles" or "flameless candles." Check after holiday specials too! People tend to buy candles the most when holidays come around so after the holidays they are often on sale. If your choosing to use something other than cups, pots, or candles you'll have to use your best judgements as to how to try and keep it in place and keep it safe.
Taking Care Of Your Tray and Accessories
Metal trays and pots usually will be designed to handle being washed and are made for serving beverages and foods so you can usually wash them like most of your of your dishes but if you add anything to your tray to make it balance better and stay putt you'll want to avoid washing off your modifications. It's best to wrap the tray and pot in a dry towel, blanket, or sheet when transporting or storing to help keep it from getting scratched, dented, or dirty and to help keep any oxidation at a minimal. If your tray starts to get water spots you should be able to use any metal cleaners to get them on. You can use a soft cloth to buff it out. If oxidation (rust) occurs you should clean the metal right away. If it's really bad you can get a fine grain sand paper and sand the rust spot away then buff the area and use a metal oil over the surface sparingly. You could also put a dab of a clear coat (preferably rustoleum brand or other rust control paints) or a color that matches your tray on the spot instead of oil. Your cups should be covered or stored upside down to avoid collecting dust and may need occasional washing. Hand washing is the best option. If you use them only for display/performance you can occasionally clean them off with a little glass cleaner to remove finger prints. Wax residue can be removed with a wax remover or by using hot water to melt the wax and then pouring it or wiping it out. If your glasses or holders have chips or cracks you should replace them as soon as possible. Especially since live flames can cause cracks to spread. Damaged glasses are accidents and injuries waiting to happen.