PetCo has their fish aquarium Kritter Keepers. 3 gallons is $11 or $12 I believe. You wouldn't have a filter with that, but you could just disturb the water regularly and keep up on water changes until you could buy one? They're only $10 anyways, so shouldn't take you long to get one.
I highly suggest rocks from the dollar store. It's $1 for over a pound of them! They're gorgeous looking, too, and haven't eroded at all. They're real rocks. For $2 your bottom could be fully covered. I boiled some water, took it off the heat, and dropped the rocks in. Once the water fully cooled, I rinsed them off super well with warm water and let them cool off, they've never done anything, not even made my water harder.
I don't know decor wise in PetCo, but I do know they sell anacharis bunches for $3 and it's a hefty amount. Mine right now has FULL GROWN anubias for $5!! Just choose wisely on whatever you pick!