First of all everyone should own at least one hammer and if you are only going to own one hammer I recommend the Estwing 20 oz Ripping Hammer. I’ve had this hammer for probably 30 years and while I didn’t use it daily like a carpenter would, I have used (and abused) it for a long time and it still is in good shape. This weight balances something heavy enough when you need some force, but still light enough for the average user to control. This hammer is available from many local store as well as Amazon Prime for less than $30. If you don’t already have something like this then is an excellent place to start and as long as you don’t lose it you will find you can pass it on to a grand-kid.
Don’t get drawn into lots of fancy “features”, the basic hammer is what you really need. If you do a lot rough framing some of those feature you might find useful, but if you know that you are way beyond this recommendation. Really be careful of a hammer with a cross-hatch pattern on it, you miss what you are aiming for and catch your thumb it will really hurt and you likely lose your nail as well.