Take a look at your watchtower raid log and the amounts of food and iron you win and lose. As long as you collect your watchtower resources regularly, the amounts taken in a defence loss will be small, but the resources gained in an attack win can be relatively huge. Allowing other players to attack you while you manageably attack back helps everyone.
But loot also increases with raid tiers:
Trophies Raid Tier
0 Bronze
600 Silver
1200 Gold
1800 Platinum
2400 Diamond
It may help to get to each threshold, but there’s no acquisitional advantage in going any further. My hope when starting a run on a raid chest is to start with about 2300 cups which should make it possible to get comfortably beyond 2400 cups after six net wins.
I’ve typically been using roughly the same cup dropping team for over a year.
My player profile indicates that my raid win streak is 100 (but that may be capped). I lose defences (cheeply) and win attacks (profitably).