Facebook/TickPick/Gametime.

Gametimes prices are usually cheapest, but they add fees after the fact.

TickPick shows you the all-in price first, fees included, so it’s less complicated.

There are lots of Facebook groups for Commanders tickets, so I assume the same for the caps and wiz. Most of those groups have rules, vouch systems, and kick people out if they try to run scams, so it’s relatively safe. I’ve bought football tickets off Facebook without any issues.