I'm fairly new to all of this but love "fiddling" with my tank setup. One thing to cut down on the costs of setting a nice tank up is to check flea markets and yard sales. I got a 10g with gravel, hood, light and filter for $5. I bought a 1g goldfish bowl with a really nice castle decoration for $2, the castle costs over $15 at petsmart, the bowl is going to be a quarrantine or hospital tank. For real plants you could always get a large goldfish bowl and grow them out.
Use your imagination, I got a really cool statue for $4 at a local closeout store, pieces of pvc pipe with the ends rounded off, heck, some nice coffee cups and add some playground sand (available at lumber stores for like $7 for 50 pounds) it's all up to you and your budget and imagination.
Edited to add: I have a 10g community with a male betta, 4 platys, 4 corys, 4 (was 8 ghost shrimp, apparently Nick likes shrimp) with a statue, tree root decoration and plants. I've got a used 20g tall that I'm cleaning and planning for my wife (no bettas allowed) and another 10g that I'm planning on as another community tank. Goal is to have a 75g or larger because she wants an oscar.