In my opinion I would start getting some extra custom classes as having some extra options to choose from can come quite handy at times based on the situation at hand.

If you think you need it, get an extra custom class slot. If not, then maybe use the token on a perk you really like and/or need.

If it's any help, I spent my prestige tokens on:

- 3 emblem and title packages (not a very common choice, but I did it)

- 1 custom class

- 8 or so guns, equipment, and perks

Now, if you add the numbers above, you'll come up with 12 tokens spent. That's because I tried to prestige during that prestige glitch we had a few months back and accidentally gave myself some extra tokens :/

I think the best choice would be to go for the custom class.  The reason i say this is because it is something that will serve useful for the rest of your time on this game.  Lets say you went for scavenger.  Once you got to level 39, the level at which it is unlocked, that token you spent doesnt serve you any good.  When i was prestiging I had the mindset of "what will be most useful to me when I am max level."  In the long run, I think you would be much happier with a custom class. 

I will go for 5 custom classes (4th prestige now) and then get all the title stuff.