Like others, I am in the same boat. I usually do some of the On Track to get a tank or two on discount. By now most of my lines are pretty far along so the discounted prices at higher tiers makes a big difference. I bought both the Emil II and Kran on discount, so I saved quite a bit.
I will be working toward the 30B. I haven't played the little BC much at all since the new lights came into existence, so I only have about 120k xp left over from the 13 90. Guess I better start playing it more here so I'm ready to go when the On Track starts...and grind some more credits. :)