I just snagged a 5 gallon tank from - of all places - Walmart. Ordered it online since neither of my local Walmarts had it in stock. 5 gallon acrylic, with a florescent light and filter included. Shipping was 97 cents. It was supposed to arrive the 17th - FedEx had it on my porch today - a Saturday - sweet! It was all of $29 after tax and shipping.
Just check Walmart's website and search on "hawkeye aquarium" and you'll find it - I tried to put a link to it here but the link is a MILE long. Others here have it and seem pleased.
I might have to baffle the filter - we'll see.
I've done numerous freshwater and even a saltwater tank in the past - I can say that patience is a virtue with fish-keeping!
You can buy the 'good' bacteria to jump-start things. In the past I used a product called Cycle. You can get it at Foster & Smith. I think this time I'm going to use the F&S knock off version of Cycle.
For my past tanks I used Prime by Seachem and swore by it - it's a water conditioner - I'll be using it again for this betta tank. Make sure the water you add to your tank is the same temperature as the water in your tank when you add it to the tank.
My plan with this little 5 gallon (for my daughter although I'm really getting into this) is to put water in it and let it sit for an hour or two today to make sure no leaks. Then I'll rinse the gravel and stuff out before I add it to the tank so it's ready to go.
I still need to order a heater, Cycle, Prime and a few other goodies - so I'll get that done later tonight from F&S.
Once everything gets here I'll put treated water in it, the heater and all and let it run about two days and then go help my daughter pick a fish.
I'll probably put the "good bacteria" in a day before we look for a fish.
Good luck from this fellow betta newbie!