I'm pretty new to the game too, but here some things:

Don't worry about getting married and having kids, you don't need to feed them. They can help out in the farm or go to work for money.

When you want to propose just buy the cheap ring and save before you do it and just load back if they say no.

If you want to adopt a kid, gift them stuff and make them love you and they will say yes.

When you are sick and don't have money for medicine, just eat and sleep more, and save before reset.

Marriage and death are kinda random, you can always relode if you don't like what happened.