i would stay away from the anenome as stated above, and the clam. they both require fully mature tanks with pristine water quality. and the thing about keeping a puffer is that they eat anything. so if you want a puffer, you cant have inverts caust theyll eat them. trust me i learned the hard way. i had a very beautiful hawaiian blue spotted puffer and it began to nip at my cleaner shrimp. another issue is the tank size. puffers can get big, a small tank would stress them out. a chiller is very expensive $300-600. for my tank, if the temp gets too high, like in these summer months, i run a fan across the top. it really helps.
some good begenner fish are Cardinals, Firefish, Gobies, damsels, and clowns.