If you have enough of a liberal majority to get the liberals into power, good. Then, promote some capitalists or clerks, and set reforms to make yourself a democracy (constitutional monarchies need to take the extra step and become a dictatorship first that is well-detailed elsewhere).

Depending how long phase 1 took and whether the Liberal Revolution happened yet, you should have from 25 to 40 plurality. Then, if you are a monarchy/constitutional monarchy/dictatorship, switch to a socialist party and wait for the 5 socialist 'Ideological Thought' inventions to fire. When you are done with the above, start buying goods needed to promote Craftsmen, Clerks, and Capitalists. This phase is over once you have a nice export income and a budget surplus, as well as a nice slush fund ready (around 50-100k is nice depending on how fast you want to implement phase 2 and your starting population.) Also, you want all 5 of the conservative 'Ideological Thought' inventions to have fired. This is so that the -25 plurality from the 5 conservative 'Ideological Thought' inventions has the least impact on your plurality, which needs to be high to get large amounts of immigrants.

However, as soon as it is available, research 'Ideological Thought'. If you have any iron or coal provinces, Clean Coal is also a must, raising coal and iron production significantly. Both raise your output for most RGOs by several hundred percent. The big ones you really want is 'Freedom of Trade' if you start without it and 'Mechanical Production'.

Focus your research on commerce and some industry techs.

This is to keep militancy down, since democratizing will upset a large number of your (largely conservative) POPs. Either way, you should work to keep a conservative party in power (not hard since most of your people will be farmers and laborers). You should stay with a monarchy or a presidential dictatorship if you start in one. Pre-Immigration, you should be focused on increasing your RGO output and keeping a balanced budget as well as saving up money for the second phase. With any immigration-magnet country, your strategy should be broken down into 3 phases: Pre-Immigration, Immigration, Rule The World.

War exhaustion victoria 2