If you're wishing to stay as a small country (yes, why not sometimes), eg 1-2 provinces, then simultaneous investments in both is the most cost effective method, since your monarch's ability will also be a big factor in your investments.
This is especially true of of normal European countries, who tend to get average or better monarchs. I tried this stradegy as one province Mecklenberg, and managed to max both trade and infra by 1600.
This is especially true of of normal European countries, who tend to get average or better monarchs. I tried this stradegy as one province Mecklenberg, and managed to max both trade and infra by 1600.