ok, first thing to read is the link in my sig 'step by step guide to setting up an aquarium' a few of us who hang out here joind together to write it so it's got the benfit of our combined experiences.
Budget will depend on what you want to do, it's largely dependant on the size of the tank, the bigger the tank is the bigger filter, heater and lighting you'll need, you'll need more substrate and more decor so it can start to mount up. It's also going to depend weather you want everything new or are prepared to shop around for soemthing second hand.
As you already have a stand I wouldn't bother with a 'package deal' type tank but would buy a plain glass box tank of the size you want and then buy your equipment seperately, already having the stand will take out a big chunk of the cost as they can actually be quite pricey.