Well that depends on what wax you are using, if you are using a pomade wax (like Murray's beeswax, which I do not recommend, they are greasy and they will make your dreads fall apart) you will have to use a lot because it does not hold the dreads together.
If you use the Let's Dred Wax, Dread Head, or Knotty Boy you will be using a finger full of wax on each dred (depending on how thick the dreads are and how long they are).

I've had my dreadlocks for over 4 years now, and I still use wax for little loose hairs, frizzes, and to condition them so they don't get brittle. But you will not have to wax them all the time, once they are about a year old.

Expect the wax to be firm and a little sticky. It might be a little hard to get off of your hands, since it's waterproof, but you can use liquid Dawn to get it off. You may find it a little different to work the wax into the dreads for the first time, if you do, get a hair dryer and heat the wax a little before you smooth it on the dread, then melt the wax into the dread using the hair dryer when your done.

As often as you please. Some people will say that you can't wash dreads at all, because they will fall out, but that is just another dreadlock myth. Dreadlocks should be washed at least once a week, just like normal untangled hair. Your dreads may feel a little loose after you wash them, but they will tighten back as soon as they dry. With new dreads you should be careful with them, the first few times you wash them, make sure to be gentle with them, after all, they are newbie baby dreads, and they are fragile.

While your dreads are new you will probably want to wear a swim cap, but after they mature you will not need one.

There are many different products out on the market that say they are intended for dreadlocking hair, but that does not mean that they actually work. Any wax that has the ingredient of petroleum is bad for your dreads, it will make your dreads feel nasty and it will make your dreads fall apart. There are 3 waxes that are appropriate for dreadlocking hair:
1. DreadHead
2. Knatty Dread
3. Knotty Boy
4. Let's Dred

1. DreadHead - This is the best of the waxes we have tested. Its strong points were its long lasting hold and its lack of grease.

2. Knatty Dread - Coming Soon!

3. Knotty Boy -this wax is pretty good over all. Decent hold. Its main problem is that it's greasier than it needs to be and the hold, while long lasting, isn't that strong. I also think the smell of their wax is a bit much. At first I was like mmm yummy, but after a few hours or so I was like sick to my tummy.

4. Let's Dred - this is an acceptable wax. It seems to be a bit pasty but it beats all the Murray's and Dax wax products. It has a pretty good hold but it does leave more it's pasty feeling behind on your dreads.