Choosing Abilities / Leveling Question

My first character that I competed just about everything I could find, topped out at level 24. 

So no, you don't have enough points to get every skill.  The idea is you will have a max of  8 active skills at any one time to choose from, in any fight, and you can swap out skills as you need for any that you have unlocked.  You also have the ability to buy a respec necklace both in Haven and Skyhold from the crafting area merchant banner, so if you want to change your mind, you can buy them, first is cheap, rest are 300gp or so each.

My way on a new game is to usually create a burner character or two, by that I mean, I create a standard character, play for awhile, swap out between all the companions and see what I like, and what skills I use.  Then I create my main play character and play the game through with them, and if it is a good enough game, then I will go through again and again and again until I am tired of it.  Each new play I will alter/change a bit how I play trying new things.

As far as your unused companions, it doesn't effect anything...all companions are about 1/3 to 1/2 level behind the Players character.

One small note:  Companions don't get their specializations until they are taken out in a party from Skyhold, so if you never use Solas for instance, then he would never get his class Specialization.