I like to carry M3 + 50 + 21 + 90, with 21mm VF 'permanently' mounted on the M3. The 50 stays on most of the time, but if I see a situation where I need another perspective, I like to have the flexibility. All of the fits in one small bag.
Leica M3/50mm DR Summicron/21mm SuperAngulon/
Canon 7/50mm f1.4
Leica IIIf/Summitar/Collapsible Summicron
Yashica Electro 35