If you're just getting started, then pretty much use what you find you like. You'll get a dozen answers from a dozen people, to be honest, and every answer depends on the personal experiences and preferences of the person you ask.
With that being said, craft paints work OK. The pigment particles aren't quite as finely ground as they would be for a paint made specifically for miniature painting, so your texture might be a bit different. They have different flow properties as well, so play with them a bit. I use them mostly for painting bases now that I have a good collection of
GW and Reaper Master Series.
Craft paints are incredibly affordable by comparison to either of these. If you want to start painting NOW, get a modest selection of high-quality miniature paint - true red, yellow, blue, green, white, black, maybe a flesh (mixing flesh is nigh impossible) - then use craft paint to "fill the gaps" in your pallette with oranges, purples, and other in-between shades of your mini-paints like browns, red-violets, and warm/cool greens. A modest investment of about $30 (that's about 6-7 quality paints and 10 craft paints) is a good starting point. Keep in mind that you'll expand your collection as you go, replacing craft paint with quality paint as well as picking up new shades.
I highly recommend the new washes from
GW, even if you use other paints like craft, Reaper, or Vallejo. Reaper makes some nice inks, but they have to be diluted ad naseum to use as a wash. The Foundation set is one that's highly recommended by many of the painters here, but I have as of yet to try them...
One thing I would stay away from though, are the
GW hobby tools and painbrushes. They are horribly overpriced and the exact same items can be found in an art store/craft department for a fraction of the price. I use a 3 pack of red sable brushes in 0, 3/0, and 5/0 and pick up a single brush at 10/0 for about $5.00 at my local Michael's (the 3-pack can be found at Wally World for a little less, but the singles aren't available at my store) and I've been contemplating some new Winsor & Newton brushed for detailing.
Remember that with most consumer items, you get what you pay for. Premium art supplies are of a better quality than average art supplies, but until you have experience in HOW they are different and which works best for you, it's best to start small and cheap and work your way up!
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One last thing, if you do try Reaper paints (and I recommend that you do at least try them - borrow some from a friend or visit a Reaper Black Lightning paint demo, go to Reaper Miniatures website for details), check out the brand new, re-formulated Pro Paint Series. They are highly comparable to the
GW paints and have a considerably wider pallette and some unique shades like metallic tints and interference colors (which are harder to find and normally cost an arm and a leg). Cheers and good luck!