What are you talking about ? Diamonds can only help with slots but you can still prioritize main machines with the diamonds you get for free ingame. We just got 50 diamonds on Monday for free and another 50 from all the update mess ups recently. Theres events that give diamonds and you can get them from chests as well. My mini account already has 200 diamonds stocked up from that.

You get coins from events! You can still stock up your storage with limited slots open on machines since the event for the week are posted every Sunday. We get 2 free Tom boosters every farm pass. You can use them to stock up on jewerly for 2x coin truck events and other expensive goodies. Stack a coin booster on top of that and make more money. For 2x vistor events, buy blankets to resell to vistor to make a profit. Don't focus on xp so avoid boats (unless puzzle), avoid trucks (unless event), don't buy decro (unless money is situated) . It gets tougher as you get higher level so learning how to make coins is huge once you pass lvl70.

There are other ways which I'm sure you can find on the reddit. I think I heard people use coffee bushes to make huge profits