This is not an idle game, it's an incremental game. Idle Farmer lets you accumulate as many crops as you want, while Farm Rush limits storage capacity. You have to constantly buy upgrades. That is known as incremental.
Salesman sell meter is far too slow, even if I get 40+ of them working on a field. Since there are only nine fields, it makes more practical sense to save up for the next field, buy just a few upgrades, then save up for the next until I can reset with prestige. The sooner I can gain prestige, the sooner I can reset, the sooner I can make it back to the last point.
Crop values are too far out of balance. Dozens of workers in the grass field won't compare to just a handful working in potatoes, so on and so forth. Once you get to the last field, there is no reason to get upgrades or anything - you reset with max prestige.
My basic strategy is buy a field, save up for 10 workers/salesmen then go on to the next. Takes me all but 5-10 minutes but requires me to start the game multiple times a day, due to the fact I have to constantly purchase upgrades and fields. That's why it's an "incremental" game, not an idle game.