The old adage holds true: boys before toys. I found that maxing out on deployment is more important than new battlegroups or upgrades to them. That and it's important to spend points to replenish your lost units. Say, for example, that you retreat a platoon of T-64s that lost one of its three tanks. See that number 5 counter next to the symbol down there? That's how many individual vehicles - not platoons - are in reserve. So while your platoon will return with full health, unit count, experience, and supplies, you can't do this forever.
