First thing I have to tell you is sub-200 farming IS NOT worth it. There is actually very little loot down there since it is mostly just newbies. Every 1 in 25 will be an advanced base but these bases rarely have collector raids and are usually better than most people can take out. Contrary to popular belief, sub-200 farming, is truly awful and you would not do very well if you dropped that low.
Instead I have ranges you should use to farm instead.
TH7: Silver One
TH8: Gold Two
TH9: Gold One
TH10: Crystal Two
These ranges guarantee you collector raids. Every so often you will find a decent storage raid off a lower TH level as well. Remember these ranges aren’t exact, but stay around them. This will maximize your loot intake. In conclusion, please, please don’t be one of the people who try to farm that low. Trust me, it doesn’t work and you will only find brand-new players down there!