Wet felting is pretty simple.
1) Get roving - many yarn shops carry it now, try a local waldorf school, look online or contact your local spinning/weaving guild for local sources.
To make a baseball sized ball you will need the equivalent of about 1 standard large ziploc freezer bag worth. I think it is about 1 pound. Here that costs about $6 - 7. You can use undyed roving for the centre which is usually cheaper and just use the dyed roving for the top layer and the decoration.
2) you also need some old nylons/pantyhose, some dish detergent and some warm water. You can get a bell to put in the middle if you would like.
3) Wool felts with warm water and friction. So basically you want to roll the ball around in your hands until the fibres "knit" together.
4) If you want a bell start wrapping the roving in small amounts around the bell. Use pieces that are about as long as your hand and fairly thin. You want to build layers. once you have a ball about the size of a golf ball, get the ball damp (not sopping) and add a drop or two of regular dish soap. Start to roll the ball in your hands like you would if you were making a ball of playdough. You will feel the ball start to tighten. Add more layers and continue to roll in your hands and add a bit of water and soap to keep it moist/slightly wet and soapy. You'll be making suds as you do this. Rinse those off so it doesn't get too soapy.
5) You can do this by hand, or once you get the golf ball sized ball done you can add more layers and put it into the toe of the nylons, tie a knot and either do it in your hands or toss it into the washing machine with your regular laundry (hot or warm water will work better). You can also use a washboard to rub the ball against to create the friction.
Once you get the main ball done, you can add a coloured layer and wet felt it, or you can needle felt the colour and designs on. Needle felting is very simple to do and you can make beautiful things with it. You can see some samples here.
You can dye the wool with koolaid like you would for playsilks, or use dye.