hvv doesn't have tickets for destinations outside Hamburg

Of course it does: the HVV region extends quite a way outside of Hamburg, and includes Winsen and Uelzen.

However, if you look at the HVV rapid transit map you'll see that the line out to Uelzen is depicted in a lighter shade, and if you look at the key in the bottom left-hand course, you'll see that this means that the HVV tariff only applies to season tickets.

But whether you're commuting within Hamburg or on this route, you're throwing a lot of money away by buying single tickets every time you travel. If this is a regular commute, you need a season ticket: a monthly pass is the usual way to do this. If you also need to travel into Hamburg itself frequently enough, it may pay to get a pass for the entire HVV area, which will give you unlimited travel on all forms of local public transport.

Usually you can save extra money buy getting the monthly pass on a subscription model, but that normally locks you into a contract for a minimum period of, say, a year. With the €49/month Deutschlandticket expected to launch this spring, you might want to go for the standard monthly pass so you can switch to the Deutschlandticket as soon as it launches.