How much are drop rates increased by?

Hello and welcome. As @Quinneczech already mentioned this question has been asked before so kindly use the search feature if you are new here. Drops are increased with no given value and that's because there isn't a general option where you set them all at once times something for a given value. There are various factors that will influence the drops, for instance some of them are left as default, however they're still increased and will drop more often compared to vanilla due to various areas that are set to have a max players drop, number of players, rng, various settings that are specific to private realms and so on. Bottom line there is no exact number for drop rates because some are altered and others are not, we have one only for the experience rate which you can check by visiting our website homepage.
For magic find clarification you can read some of the recent threads like this or this (many others if you use the search function too) and check the guides too. Enjoy your stay!