Hi, I''l add this for the meantime, but I'll write more as and when I've more time to...
+study the colour wheel when choosing a colour for your army: look at complementry, contrasting, and pick your neutral colours. excellent colour theory link:
http://www.brushthralls.com/tutorials/2.html+when you've decided the main colour for your army, buy as many shades of it as you can afford: it'll help vary the colour palette and enrich the depth of the painting
+conversely if You can't afford many shades just buy the darkest and follow the next tip, its nearly always possible to ligthen a colour but seldom can you just darken it with black!
+Add either bone white for a warmer shade or a blue/ grey white for colder finish when adding highlights to colours. Don't use skull white unless you have to!
+If you can't afford lots of expensive inks just buy chestnut or smokey ink as it can be used for most colours
more to follow...