Really anything, you could do it without troops, but that would take an ungodly amount of time and is no fun, I did a mix of both where I started by taking a lot of land and then just buying the rest as that was quicker than fighting, also less laggy.
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btw I almost got France as Luxembourg on imposs by teaming w/ belgium and German empire. France pulled out great Britain and Russian Empire. then apparently the Baltic countries and Scandinavian ones attacked Russian empire and then ottoman goes LETS GO KILL RUSSIAN EMPIRE. in the end we had a world war and I got destroied. rip map