First, don't buy points unless you need them to keep others from expiring or if you just need a few to top up the account for a redemption. They are a terrible buy. In most cases you can just book the hotel for money cheaper.

I would focus on one or two programs to get started with, because you must add points to each a program on a fairly regular basis or lose them. Hilton will wipe your account clean if you do not have activity in a year. So focussing on a few makes it less likely that you will forfeit points.

At 17 you most likely do not have the ability to get the big credit card bonuses just yet. I am also assuming that you are not going to be able to earn via hotel points since most require you to stay and pay for a room in your name. I know that I could not do that at 17.

Although SPG is my favorite program, it is ver difficult to get SPG points if you are not staying in a hotel or using their credit card. While you can get a few points from a non stay related meal in some restaurant, I find that these rarely post correctly on their own. So I would leave SPG for later and focus on Hilton and maybe Marriott. Marriott will forfeit your points after two years of inactivity. That is a recent change so ignore the older posts that say they do not enforce it. They now do.

Both of these programs have shopping malls where you can earn points on the things you are ordering online anyway. An occasional purchase in each shopping mall will keep your points alive. Also, if you have a credit card (an authorized user card on one of your parent's cards should work) you can register it for the HHonors dining program and get a few points when you use it at a participating restaurant. This only works well in cities where there are a variety of restaurants signed up for the program.

Pretty soon you will likely be headed to college and may have some hotel stays on your trips home etc. I know my kid had an overnight stay every time he did the 20+ hour drive between home and school.

And welcome to Flyertalk!