apps I use 

Chase Sapphire Rewards - affiliate link with which you can earn 60,000 bonus points with a Chase Sapphire® card. The card I use almost exclusively.

United MileagePlus Card -  Choose any United MileagePlus® credit card. I can be rewarded too if you apply here and are approved for the card. 

Uber affiliate link for 50% off 2 trips (max $10 savings each ride)

Lyft - affiliate link for 50% off 2 trips (max $10 savings each ride)

Curb - affiliate link for $10 towards your first ride with Curb. This is a taxi service and has standard prices without the sometimes hiked-up prices of Uber or Lyft. It is offered in most cities.

UberEats affiliate link for $15 off first order over $25

Rakuten - affiliate link for cash back on online shopping trips at many places

Yesstyle affiliate link - for Korean skincare (eg COSRX), sunscreen, and makeup (eg IOPE, Romand)

Express & J Crew - affiliate links for work clothes

Amboss - free month of amboss access with my Ambossador code AMBOAY2425-40Z8 (I get nothing in return for promoting this. I think they're great to use as a medical encyclopedia, especially during medical school). Let me know if the code expired, I can ask for a new one.