Follow this advice!
From my experience, THE BEST IS ENEMY OF THE GOOD, I mean: as everybody seems to follow the BEST resource guide, you'll find it hard to find trades and get the 3BR (just because you have RUBBER), on the other hand it will be much easier to get the 5BR or the 8BR!!
In any case, if you manage to fill ALL your trade slots, even without bonus you'll be fine and would be much better than having them empty just because you're looking for something special that you don't find (you can always change it later).
I'm in top 1000, 3,5% nations without any problems, higher nations are there mainly because of tech trading and buying donations not because of the trade set, and once there it's easier to keep on top with cheaper infra cost and upkeep than with higher pop.
If I were you I would start trading (for anything) NOW!!!, you're wasting more time and money than you think, just start playing and you'll have plenty of time to try for yourself.... But it's your decision!!!
