A few points, from someone who has been around here a long time, has left for greener pastures due to vehement political disagreements with the administration, and come back:
- The perfect is the enemy of the good. Don't try to get all the details perfectly correct for your timeline, just write. If you get something wrong, great! Actually writing a timeline and accepting feedback on it is a great way to guide your research. If you only have good research for the first year or decade or century of your timeline, write that much, and see how things look from there.
- The beautiful thing about alternate history is, at a certain point, other than the broad outlines, all research on actual history is of little use. So don't worry if you're not as well versed on the details of history awhile after your timeline starts; it likely won't matter as much anyway.
- Stay focused on your topic. Its too easy to get bogged down in the rest of the world, particularly insofar as you have to leave your area of (relative) expertise.
- Just stay out of political chat, if you're here for the alternate history. Its just easier that way, and, odds are, you'll have an easier time maintaining some level of respect for your peers on the site.
PS: I want to take
Politeia Tōn Rhōmaiōn as far as possible, so shameless plug.