Around 50 mg should be the standard scale for any new reaction.
Use the following guide to modify the quantity depending on parameters listed:
Scale up: factor of 5
When scaling up a reaction do so in orders of 5 magnitudes (of weight) maximum.
Note! On very small scale the yield might not be reliable due to the presence of small impurities/solvents/variations in the balance which result in a higher than real yield. When scaling up these variations are not as relevant so the yield might drop. Alternatively, on a larger scale being able to remove these impurities more easily in the starting material might lead to a higher yield on scale up.