Don't let a bad round of tee swings discourage you. Like BPH said, hitting off a tee is all about setup. People tend to place the tee to far outside and too far forward when they first try it which leads to lunging and a disconnected swing. Keep moving the tee around until you find a spot where you're consistently making hard contact.
If I hit off a tee (I haven't in a long time), I use wood bats only. I can hit them over 300', but it takes a good swing.
When I hit off the tee I'm looking to consistently spin the ball rather than yoking out and bludgeoning everything.
I do both of these. I move the tee around so it works directly for my swing path and sweet spot (so I think). Once I figure out the spot, I try to recreate that a couple of times (10x). Tee work for me - I look to hit line drives with distance and very good solid contact (gap shots to be exact).
As someone said before (not sure if it was a video or an article), when in a game if you're early its down the line. If you're late, its kinda up the middle. If you are spot on - its a gap shot. More so, if you miss slightly - its a hard grounder. If you cut it slightly - it has a possiblity to go out.
I swing a 30oz (1 piece/balanced) for the first couple of swings (10x). Then I move to a practice bat (28oz/0.5end load) that is similar to my gamer. Once I think I have it down - I then take about 10 swings with my gamer (27oz/0.5end load). I don't over swing with my gamer, as I want to feel my body/mechanics. I take a bunch of cuts that are 'soft' and the ball flies if I have everything else correct. I look for the swings that make the ball move with very little forceful effort.
All of this has helped me translate it to good game swings. I notice right away in a game if I am ahead, or if my step is not inline with my swing/snap. I also am very aware of how my gamer bat works, and if I miss the sweetspot or simply miss the ball slightly.
If you get all of that... use your first AB to figure out where to stand to get those off the tee swings. I did that tonight. My first AB was a line drive shot down the line. He was throwing me short and I was reaching. Next AB, I let it go deeper and I drove it through the right side - but he was still throwing me shorter than were I place the tee. Last AB I moved up in the box - sent a bomb over the fence.
Hopefully all this makes sense.
Good luck!