For the early game, your economy is going to be stone-based.
On the other hand, trade routes don't get blocked but you have to follow a path (or pay to go "back" on your path and start another one) but aside from a few specific nodes the rewards aren't that great and just leads to a better economy, a few reward chests and maybe a victory point or two if you really invest.
I think there might be alternative entry points for 2nd tier techs, but those obviously cost more. This includes tech that is past the initial ones, meaning that you can get fucked for second tier techs unless you snag a first tier one early on.
Technologies get blocked off if someone else researches it before you.