What are the optimal percentages for analog system

This is a little complicated especially not knowing your budget and how far in your upgrading you are prepared to go in the near future. But I agree with those who suggest you get the best table you can. Good $200 cartridge will sound OK with $2000 table, $1000 arm and $400/$500 phono stage. With decent cables of course. You could also consider voltage stabilizer/conditioner or/and motor controller. Turntable can last for a very long time.
I personally would probably wait and upgrade everything at once and would spend at least 50% on the table alone.

Where should most of the money go...cartridge, phonostage, or table?

Imo, the priority goes like this: Table, Arm then Phonostage then Cartridge. For now, with your current gear, I agree with Elizabeth. What price range were you thinking?

There are no hard and fast rules but something like this might be a fair starting point:

Table/Arm- 50%
Phono Preamp- 35%
Cartridge- 15%

IMO
YMMV

Thanks for your responses. It seems like I should start with upgrading the phonostage first. I'm looking to spend about $500 on a used unit.