Easiest way, for about $20, is to buy an Estes starter kit, IMO. It will come with a rocket, an engine, a launch pad, and a launch controller. Actually, everything you need to launch a rocket ... once.
http://www.estesrockets.com/categories.php?cat=starterLots of hobby stores carry these, and even some crafts stores like Michael's.
It's very easy at this level. Things to be aware of when buying a starter kit:
1) There are varying degrees of difficulty, ranging from rockets already completely built, to requiring very little effort (ETX, I think), to requiring a little more skill (Level 1, 2, 3).
Also, when you buy a kit, you will want to buy extra
engines. Look on the starter kit package to see what engines the manufacturer recommends for the rocket. They usually come in packages of three. Two or three packages should be sufficient for your first time out. I usually get some in one of the lesser power sizes (like 'A' or 'B') and also one in a higher power ('C' or 'D'), depending on the recommended engines for that particular rocket.
I also always buy an extra package of
igniters and an extra package of
wadding.
You'll probably need some white or wood glue. I doubt you'll need paint unless you get a Level 1, 2, or 3 rocket. Actually, I think it's not so much skill as it is patience.
The thing about rockets is it can be a lot of fun for very little effort and money. Also, it's a very fun thing to do with kids.
I only get involved with it once every year or so, and then I put it aside for awhile. It is not satisfying on the level of shooting, but it's more relaxed, cheaper, easier, at least at this level. You can build bigger, more powerful rockets, and you can design your own. Both of those paths take more money (but not much) and involvement.
The starter kits make it pretty foolproof. Observe carefully the instructions regarding putting the igniters in the engines. Estes, I think, has a great page on their web site about igniters. But, even if you do it wrong, it'll still work half the time. It's easy to do right, and easy to do wrong if you don't read the instructions.
This is a hobby that scales up. The small rockets that use 'A' and 'B' engines cost about fifty cents per launch. It's hard to beat the cost with any other hobby. My 'D' engines cost me $5, I think ? They are for bigger rockets. The 'E' engines I bought for my Aspire cost me $11 each.