Welcome to the forum and welcome back to the hobby
Personally, i'd start with infantry. Get a nice box of 10 for somewhere around £20 and practise the basics - brush control, layering, washing and highlights. That gives you 10 models to get to grips with the various techniques. I wouldn't go onto painting hero models until i knew what i was doing. £15 on 1 dude isn't logical if you cant use some basic techniques.
If this is your first time back, i have to ask - Do you have any paints?
If not, look at companys like Vallejo and Army Painter for colors. The
GW colours aren't great.