Getting started...
First and foremost, the main theme is CHEAP! Most the stuff I use is either left-over from another job, or bought cheaply. For example, to varnish figures, I use a polyurethane boat varnish originally bought to treat some wooden stuff in the garden. It wasn't cheap to start with, but once it becomes "left-overs", it's free for modelling purposes :)
I often read "How to paint..." this that and another for figures. They always seem to use well-known brands. OK, if you're a sharp painter, stickler for detail, like painting the eye-brows on your 2mm Roman auxiliaries. I use acrylics bought from a local "cheapy" shop. It's a box of twelve basic colours. One thing I've learnt from reading military history, is that there are "official" colours and then there is real life! You see painting guides that say use this colour, that colour and mix these two. But then you read up that the uniforms faded or discoloured quickly. Heck, I remember my socks in the army - I was give about five or six identical pairs of socks. after the first few washes, I couldn't get a single pair to match up! And modern manufacturing processes are supposed to be better. Even if today's DPM doesn't fade or wash out like its predecessors, in the field it will get cover with dirt, dust, squished plants, plant stains and what-not. So, if you feel the colours look right, and your happy, go for it!