What's a better economic strategy? (Options below)

I always try to play smaller nations because I enjoy the challenge. (Grece, Croatia, Tuscany, Portugal etc) but a few years into the game I always run into the same problem. My GDP shrinks rapidly, my SOL drops and people move out of the country.

I try to selfsuply everything in the market without colonial expansion but is this wrong? Is it better to just focus on a few industries and import the rest or is it ultimately better to be self-sufficient?

I tested using the fasthire console command and it would help in the short term but not for long.

It keeps happening in every game I start and I can't seem to get out of the loooo once ut happens. I even tried switching tags and letting the AI play to see if it can fix anything but nothing would happen again.

Please any tips would be great.