That all depends on how much money you have to throw at a set. The smaller the tank the more maintanence but, IMO Its not that bad. I dont think its a bad idea to have one that size as a beginner tank. I think it teaches you good house keeping.
As far as the blenny's go, yes they can survive in a tank that size providing they are not the pod dependant species. Blenny's and dragonetts are often placed together in the same catagory. Blennys like the Midas and the Bi-Color are not micro fauna eaters although they wont pass up a pod if it happens to be in their way. Their diet consists of flake, frozen or pellet foods. They are more often seen swimming in the water column and are known jumpers.