My incoming TDS are about 300 and I started with a 5 stage RODI from AirWaterIce. Over time my water volume requirements changed and I've made the following additions to the system:
1. Added a 2nd membrane which filters waste water from the first membrane. This has increased my output while also reducing the % of waste water compared to final product.
2. Added a booster pump. Someone else asked about your pressure. That's a good number to know. If its very low my understanding is that the membrane will not perform optimally. I have about 80PSI now going into the system.
3. Added an additional canister of DI resin. I make 100g at a time so I don't like to stop production in the middle of a run to change out the resin. Having 2 resin containers allows me to fully deplete the first canister without worrying about making water greater than 0 TDS. Once production is complete, I take the 2nd canister and swap it to the first and then refill the 2nd with new DI resin.
I've also added an inline TDS meter which captures 3 data points. This is helpful because you can see TDS going in, TDS from the membrane which helps determine when it needs to be replaced, and final TDS of the product.