>>73082883you can:
Learn tile efficiency (discard better): Read the related chapter in Riichi book 1 or use this
https://euophrys.itch.io/mahjong-efficiency-trainer to train (not good when you know how to play as pure efficiency is not always the right call)
Learn to identify more yaku, you probably already know the basic but
https://youtu.be/HbWKs7KRUkgcalling Dragons/seat wind/round wind is great if you have doras
picrel are some beginner yaku, simple and effective,you can find a complete list just by googling Yaku List
Defense: when you know you're hand sucks (low value, far from being complete), it's late in the round, then it's best to just survive: to avoid dealing in, just discard what someone else has already discarded, every discarded tile that went through after a riichi is safe (read related chapter in Riichi book 1 for more advanced defense)
Learn 5 block theory