I'm sorry to say but you shouldnt jump to what everyone says on here, I would have to dissagree although the tank you have isnt sufficient enough if you get a tank of 30 gallons or less you need to be very carefull, if your looking to do this cheap then do not get an anenome, they require specific water conditions and without a skimmer, which are not usually very cheap unless you find a used or crappy one then your anenome may run a high risk of perishing,.. anenome, lets just say they are not easy at all, you can get easy species for okay water quality which is what you can afford because most of the time expensive goes hand in hand with good water quality. but almost all spcies that co-inside with clown fish are hardy but hardy in good water conditons. and a tank of 30 gallons or less is considered a nano and a nano will be more expensive to keep plus the things you will have to test/ add to make you anenome happy, so i would still get a clown fish or a pair if the tank allows for it, and suppliment the anenome with a frog spawn or a coral that looks identical to an anenome but isnt as expensive and hard to take care of for a beginner, and your clown fish will probably host in it, its more rare to have one not host in it, and some advic if you get a coral make sure it doesnt have a stony or hard base because they can scrape themselves on it leaving an unatractive blemish and with a coral that is easy you might get away with cheaper lighting too.
True you can have a perfect tank for cheap. minus the live rock, inverts, cleanup crew, and fish.
i have 280 dollars of live stock in my tank and i dont have alot some was given to me. the things you put into your tank are expensive plus monthly maintinence and additives and tests, but dont be scared to start one up because your missing out they are great just make careful choices and calculate future budgets if you get certain things that require monthly things added. just try and go for easy things in the beggining a small tank isnt easy. unless you have money to maintain one that isnt abusing your fish's habitat which is the water. sorry i just babble on but its all true if you kill an anenome its usually not a cheap mistake