What kind of gas does it take and what kind of oil do you recommend?

Hello,

BMW recommends to use of premium gasoline on this 525i. So you need to use 91 octane or higher.
For the engine oil you should use 5W-40 Full synthetic oil, preferably with 'Euro spec' but it is not required. Any good quality full synthetic oil will work (like Mobil1, Castrol etc.,). It takes 6.75 quarts of engine oil.

As for the air and oil filter I personally like to use the factory ones that you can get it at the dealer or you can also buy form Amazon. If the OEM filter is not available you can use the Wix brand filters, they are very good quality.

https://www.2carpros.com/articles/how-to-change-engine-oil-and-filter

Please let me know of any questions you might have.
Thank you.