About the best paste to use for gpus is Arctic MX-4, but some ppl also like Thermal Grizzly Kryonaut and CoolerMaster MasterGel Maker.
You can't just use any paste on a gpu. Your cpu has a heatspreader made of thin rough metal on it, but the gpu does not, it's direct die silicon, almost glass-like. So the thinner, liquidier pastes tend to run right off with heat and fan vibrations and pressure from the screws which will leave bare spots on the die itself.
You'll need to use thicker pastes that do not dry out, definitely Not Arctic Silver 5 or similar. Just something nice and thick and will stick to the gpu die.