I'm New. It seems like I should ...

Lert: The problem is that your MS-1 won't earn XP that you can actually use on your NC-31 and Loltraktor without you spending gold to convert it. That's the difference between tank-specific XP and 'free' XP. Free XP can be spent on any tank, tank-specific XP only on the tank it's earned on.   So, yeah, while your MS-1 could fund upgrades on your NC-31 and Loltraktor and FT, your MS-1 won't be able to unlock those upgrades. And your NC-31, Loltraktor and Ft will earn enough money to fund their own upgrades to begin with.