If you are on a budget then I would first recomend that you go with cold water fish.
ie, fantails, comets, white cloud mountain minnows, danios, corys, rosy barbs, celestials, inanga, etc.
the bigger the fish you get the bigger the tank you will require. a nice size tank to start off with is a smallish one of about 54 litres 60 x 30 x 30cm
you will need also require the following
- filter... Hang on Back ones will do nicely and not very expensive
- Gravel
- Plants
a good beginner fish I would recommend is the White Cloud Mountain Minnow, as they are very easy to look after and will breed quite quickly
Hope that helps