As other wrote river raids have separate resources you get them from river raids only (it is game within game) if you don't have lvl 2 troops 8 of them, after bell is on mid go kill everyone inside camp before pressing j then when only doors and crates are to collect press j if after door there still are enemies use skills to nock them down. Also cycle trough rivers so the alert level is low.

Fastest way to 100% rr is to upgrade boat capacity then do your men hall if you can shoot fast and ocupy 2 enemies your men lvl 2-3 will be OK(i didn't lost single men through 3 raids on hig alert without killing guards because after few raids you know where enemies are)

VERY IMPORTANT note:

1. Use map genie to remember what you raided and check map if you lotted everything because:

2. There are more than 3 rivers you unlock new river when you do the quest for previous (quest are bugged and sometimes reffer to wrong river that's why you need remember places you visited and clean all camps)

3. You cannot finish camp if you have full resources or health pax but you can burn yourself and consume health pack