If you're going to do some serious furniture building, you might want
the jointer first. You'll want a good tight fit for those table tops.
My 2 cents.
Joe

If you're into serious furniture building, you want both.

To the OP: Don't sweat that statement. You don't want two new tools to learn
at once anyway. One tool at a time. Yoiu need to fiugure out what you can
and can't get away with on any piece of machinery. That just takes some
quality time.

IMHO nothing looks more amaturish than a piece build from exclusively
standard dimmensioned stock (e.g., all 3/4")

3/4" drawer side look positively dopey on a smallish piece like an end
table. To avoid this, buy a planer.

I bought a planer first and I still think that is the best way to go. Then
when I got a jointer, the accuracy of all of my cases magically improved. If
you think about it, just about every cut you make is referenced from some
presumbably straight/square/flat edge. If you can establish that edge from
the beginning (that is what a jointer is for) you have a much better chance
of having a tight square carcass,drawer,box or door.

Planer first, try not to wait too long for the jointer.