Use your crystals to help buy extra repair droids. A 4th (or 5th droid) really helps in the rebuilding process more than crystalling build times does. Also, when you hit level 9 it really helps to have at least two free droids to repair both your sentinel and oppressor dekas. I rebuilt myself and my strategy was to skip researching all those units that were gathering dust in my old HQs. Instead I focused on leveling up as quickly as possible skipping stuff I knew I wouldn't need in the future (researching only the units I was using at my old base level). Once I got back to where I was I took the time to go back and research some of the old units up and now throw them in the mix occasionally to do something different. Also some of them got a buff after the fact so it was good that I went back and upgraded them later.
Member ImperialNWA Andriod / IOS Imperial Squad
LINE ID is python6swc