Any Tropical Fish keepers on here - Advice wanted.

I am hoping that there might be a few Tropical Fish keepers on here that might be able to help me out with some advice suitable for a complete beginner.
I have a fairly large aquarium on offer to me (3 foot x 18 inches x 18 inches complete with hood and lights) which I would like to set up with tropical fish. I would like advice on which heater, filter, air pump etc to get as well as details for "cycling" and which or how many fish it would be best to have. (I'm not thinking of going too "exotic", just "run of the mill" but fairly colourful fish which are not too expensive or dufficult to care for - really just something to brighten the place up a little)

Many thanks in advance and Best Wishes for a Happy Festive Season to all!