If you had Velvet in that tank and there is currently nothing in it, I would bleach it, rinse it off thoroughly and start from scratch...or you can let it sit empty for 76 days. Sanitizing it and starting over would be much quicker, depending on how long it has sat empty already.
Either way, you may want to look into quarantining your fish before you loose anymore money. I had over $600 in a QT that had Marine Velvet and since they were already in copper before I noticed it they all made it through. I've dealt with Velvet twice, Ich once and two bacterial diseases in QT with minimal loss and my DT is clean from the start. With the amount of money we all put into this hobby it should be pretty easy to justify the additional cost for QT Tanks and medication. Just my two cents though.
Edit: And as far as cheap fish, I really like Cardinals and there are several different types mostly around $20 or under. My favorites are Banggai and Pajama. Not sure about schooling, but I have a pair of each. I also like Dottybacks and they are pretty cheap, but I think you could only do 1 or 2 in that size tank since they are territorial. I have tried to get a school of Blue/Green Chromis, but twice I have bought 8 of them and I am left with only three.
