To return to the specific suggestions to Bttocs - after you've picked whatever basic wax family you will be using this winter - we'll assume for example Holmenkol - get 2 or 3 of the big blocks (150 g) of Beta and 1 each of the Alpha and Ultra. You may be able to hook up with other parents to get bulk order discounts or savings through your coaches or some of the sponsors here. However, you are going to find situations where the skis don't glide as well as usual - pay attention to those days/nights and collect some info: what was the SNOW temp (you can get a little digital probe for about 20 dollars), was there new snow and was it natural or man-made (often at a resort, they make new snow almost nightly during the early season, sometimes mid season, and less late in the year), has the snow been through thaw/refreeze cycles, what was the snow humidity. The digital hygrometer for this is expensive so what I do is get a feel for how much moisture is in the snow you are skiing on. When it is not too cold, a snowball test works fine for me - if you can pick up a handful of snow and make a snowball with one hand it is very wet, if it take 2 hands it wet if it stays together very solidly and medium if it forms but does not get real solid, and dry if it is hard to form. As it gets colder, the snow can still be wet but the test results shifts down so that if it is 0 and you can get anything like a snowball forming, even if it falls apart easily, the snow humidity is pretty high. One of the biggest factors affecting this whole process in MA will be the snow making practices of the hill you are skiing on mostly. Some places blow wet snow right onto the trails right before training and just groom. Others "cure" the snow after they make it to let it dry out. Some blow big ice crystals, some small. But most places do the same thing most of the time.
The reason this is important is that there are a couple of things you can do to improve the performance of the wax through additives. The basic additives are:
Fluoros (in Holmenkol's case GW 25) which make the ski faster in wet snow conditions. At your son's level, I'd recommend not bothering with this. You need respirators to use them and they are expensive.
Graphite/Moly - Holmenkol makes a moly/graphite additive which works very well in wet, dirty snow that has been through melt/refreeze cycles, it is also supposed to work in very dry cold snow to reduce the electostatic friction (although I have not found it best for that). The moly is tricky because I have found that it can sometimes make the skis much better and sometimes a bit worse. This is why you want to keep some kind of a record of your prep and experience. Anyway, I'd recommend getting one block of this and trying it if you hit that kind of conditions regularly. (Last year I used it a lot). Just rub it on the base before waxing (like a crayon) and then drip the wax on top and iron. It does not change your iron setting. You can see what thickness of rubbing on works best for your hill's snow.
If you want to get a bit more exotic but you probably don't need these.
FluoroGraphite - Dominator SRB - I have found this to be the best for grabby dry snow (other than new dry snow), either crayon on before waxing or apply in a checkerboard pattern with the wax (described on the Dominator web site). I wear my respirator when I use it. A little goes a long way and it is fairly expensive. Temprerature specific. So don't bother with the warmer one to start just the cold or extreme cold
Micrographite - Dominator FG - these are for new snow, apply in the checkerboard pattern with the daily wax. These are moderately expensive but good for that new dry snow that can be real slow. It won't help much in a super wet new snow without fluoros so I would just get the extreme cold or cold if you want to try it.
Another suggestion is to recognize that sometimes you are just going to miss the boat entirely in your wax pick. For these situations, you might want to get some rub on waxes that you can do right at the hill. Pick one company (I use Dominator's Momentum) and use a nylon over a cork brush to get better adhesion. Brush a little after applying. Hope this helps get you going. Others may have better ideas but this would be what I would do.