What advice would you give to people in their 20s?

Don't assume you have to get on the relationship escalator of "dating - exclusive - engaged - married". There are other kinds of relationships, including no romantic/sexual relationships at all. Don't stick with someone who's not making you happy out of inertia or a sense of obligation.

Be social. Don't burn yourself out socializing every night of the week, but if people are inviting you to be a part of their life make a good effort to show up. Video games or YouTube or whatever will always be there. Friends won't. (This assumes the social stuff they're inviting you to isn't , like, insane. Skip on someone inviting you to do heroin or whatever.)

Pay attention to your spending. Some people like a dedicated program for budgeting, or their bank provides something. I'm a particular kind of nerd so I used Google sheets. Whatever you use, adding up what you're actually spending every month can be illuminating. I don't expect anyone to discover "if I stop getting avocado toast I can afford a house", but knowing where your money is going is an important prerequisite for controlling it.

Don't fall into lifestyle inflation. Like, a friend of mine started making good money and his budget grew. He was spending $1000/month on food because he'd just gotten used to dining out and such. His paycheck was bigger but he wasn't saving any more. Another guy I used to work with told me his family "struggled too" despite a $500k family income. They had a big house, new cars, expensive memberships, extravagant vacations, designer clothes. You can just not do a lot of that and be happy, too.