Hello there iv just bought a tds meter to test my tank water. What should the meter read to be of good water quality for my oscars?

Load of adds on the net but no clear results...
Can't help you out!

You realize it just measures dissolved solids in the water column, great for salt and breakish setups. It also depends on what it is exactly that is dissolved in the tank water.I would find out what the tds of the part of the amazon oscars mainly come from.

the gadget had no use in happy fish keeping. fishes doesn,t care what dissolve solid
was there in your tank. what matter most most is the data for ammonia, nitrite and
nitrate. pH is not that critical as long as it remains stable...

so the point is: what you need is a liquid test kit, not a tds meter.