A quick guide to the Geoscape on classic:
-Spam satellites early. As much as your engineer capacity will allow you to build(in terms of uplinks and nexus).
-While you're waiting for the satellite stuff to come online, build an officer training school and a foundry to tick those boxes off. Foundry isn't strictly necessary, but it's so cheap that it doesn't really matter. Build 2 labs as well, it will make the research times on a lot of the things you need come down. If you're waiting 2 weeks or more for something, you're doing it wrong.
-The rest of your money and resources go into gear, all of it. If you feel like you need a stepping stone for weapons, get the laser rifle, but don't bother with beam weapons further than that. Plasma weapons and alloy shotgun, armor, advanced fighters... stock up on all of that. Buy in bulk, just watch your ellerium.
That's it and that's all. I think I have about a whole level total in how much of the base is unused and it will stay that way. What's the point? Scientists and engineers come through satellite coverage and missions. Similarly, I didn't bother with most interrogations/autopsies. They just clicked over to "instant", which was an unexpected surprise. This sort of pace adds up. Mutons JUST switched from light to actual plasma rifles, I still haven't seen a heavy floater... And I'm already in titan armor and have been using different plasma stuff for some time. Seems obvious now, but I was stumbling early.