I (22) probably don't have the most experience or most educated advice, but I am a poor student who has only very limited funds to live off each week, so I have some advice, things I had to nip in the bud quite quickly.

• Reduce eating out, and learn how to cook. Not only financial, but a part of learning to look after ourselves properly. I struggle the most with cooking. Even taking lunch with you to work, or snacks for a long drive, that sort of thing goes a long way.
• Reduce how much "stuff" you buy. My rule is I wait a few days to a week and see if I still really need it. You want to reduce impulse buying.
• Keep track of exactly how much you are spending each week. This will give you an indication as to what expenses you can cut down on most, and which expenses aren't too bad actually.
• I'm an introvert and don't go out, but I know that this can be a massive expense to a lot of young adults our age. So if going out is your thing, then watch your expenses whilst doing so.
• Oh, and I know quite a few other young adults who also buy way too much useless stuff online, so nip that in the bud, too.

I also try new hobbies and activities by myself and with friends/family that can be done for free. So I can look forward to and find meaning in activites that don't cost me money. For me its walks outside and finding new tracks and trials every weekend, but it could be whatever.

Also, if you have someone older than you, family member, mentor etc that is good with money, it might be worth learning what they do. Have a good role model.