I like it. I believe a lot of the plants will grow and fill in after a while. It'll go faster with fertilizers, too. As someone else said, java fern is good. It grew out nice and bushy for me pretty fast! I super glued it to a piece of wood.
I have this cave and my cories love it and it adds to the natural look.
>I also hadn't considered the pea puffer - I think I read somewhere that they don't mix well with Bettas, with both of them being super aggressive.
Sorry, I meant as in you could house either the betta or the pea puffer, puffers will eat snails however so you can rule those out as tank mates for puffers.
>can I change the setup of my tank (replace fake plants with live ones and gravel with sand) after the cycling is complete?
Yes you absolutely can, in fact the easiest way to do it is
All of your beneficial bacteria is within your filter, so no need to worry about losing any during water changes.
Then simply pour your rinsed sand into the tank to about a 1-1.5 inch depth uniform around the tank (you would not need any more than 3 lbs most likely, you can buy a 5 Lbs bag at Petco or Petsmart ~$5, any brand will do) and plant your new live plants in your preferred arrangement. With most plants like Java Ferns or amazon swords, planting it is simply pinching the bottom of the plant, gently shoving it into the dirt, so its roots are in the substrate and you're done!
For a solid 3 gallon newbie live plant set up, grab 3 small Amazon Swords or Java Ferns or a mix, and one Medium of either. If you're feeling bold and want a little bit extra foliage than that try out a Anubias Nana. All very easy to care for with no concerning light requirements and all of their nutrient requirements will be taken care of by your fish and possible snail, do not be afraid to slightly crowed the plants together, they do not necessarily have spacial requirements.
>extra maintenance for live plants and difficult to clean sand vs gravel
I've actually found that sand is much easier to clean than gravel, especially white sand (helps by showing the waste a bit more clearly). 99% of the waste will sit on top of the sand instead of bedding itself under it like with gravel. To clean sand with a gravel pump, just hover it slightly over the sand and allow the suction to pick up all the debris, avoid too much sand getting sucked away into the gravel pump, you'll just have to replace it eventually. Plants will also help clean your water naturally by absorbing the nitrates (final product of the Nitrogen Cycle). Leaving you with a healthy kind of self sustaining tank.
I've been into the hobby for about two years now and actually just upgraded to a 75 from a 30, I can personally say I will never go back to gravel! It might be easier to start out but long run its much messier and a total pain in the ass to clean properly. Also, plants thrive in sand where they may struggle in gravel.
-With that kind of set up, I would recommend doing a 15% weekly water change or a biweekly 25% water change. It's a small tank but bettas aren't that messy and your plants will be doing you a favor.
-Other natural decoration you could consider would be smaller Lava rock, Driftwood, and Coconut shells for your fish to hide in. All readily available for moderate pricing at most local pet stores, especially commercial ones. It's pretty crucial for your little buddies happiness that they have at least one place to hide like a cave, but it is up to the owner what the spot is (artificial or natural). Most of my caves for my cichlid tank are artificial rock looking caves, sometimes fake is just easier.
I hope this helps, sorry its so wordy!
P.S. I would love to see what you end up doing with you tank!