Planted Nano Tank Suggestions?

[Proud Pastry]

Hello :3

I've never had a planted tank before, and I'd like my next tank to be a 30g planted tank for when I finally get a larger place (then hopefully later on get a 70g ).
But for now, just to experiment and see what I'm doing before going all out with a large tank, I thought I'd try getting a small one, like a 2.5g, plant it, and then get a betta fish for it

Anyone have any good suggestions for plants, substrate, ect?
Do you think I'd need a filter for this small tank since it's planted?
Would a 2.5g be big enough to get a betta fish and maybe a small bottom feeder?

I'm very limited with space at the moment but if I can find a larger tank (like a tall 3g-5g) then I'll probably get that instead

Any information and advice would be very much appreciated! ^^
Thank you for reading!

 

[Ps3Steveo]

A clay based substrate would be good as its porous and soaks up excess nutrients, still run a filter otherwise the plants wont get the ferts, I'd go as far as just a betta in a 2.5G but be careful with flow as plants need a lot and betta's dont like a lot.

 

[Questions?]

anachris is really good. i don't use ferts, or co2 and it grew literally a couple of inches overnight