I like the UN list (plus Vatican City obviously) of 194, and think it's a no-brainer to add Kosovo and Palestine since they're both recognized by at least half of UN members...so to me that makes a "must do" list of 196.

There's another 19 places I think are pretty independent, based on independent border controls, currencies, judiciaries, and parliaments:

Abkhazia, Aruba, Cayman Islands, Cook Islands, Curacao, Guernsey, Hong Kong, Isle of Man, Jersey, Macau, Nagorno-Karabach, Niue, Somaliland, South Ossetia, Taiwan, Tokelau, Transdniester, Turkish Cyprus, Western Sahara

So that list of 215 is what I'm working off currently