I would say, do fast two-lane roads first.
Once you’ve gotten used to the speed and the different steering inputs required at speed, then you can add the freeway experience which adds merging traffic and high-speed lane-changing into the mix.
Leave at least 2 seconds between you and the car in front; 4 seconds in the wet.
To do this, you watch the car in front of you pass a fixed object at the side of the road (e.g. a road sign or whatever). Then you start counting in your head (or aloud as the mood takes you): One Kangaroo, two Kangaroo (or whatever long word you want to use), spoken at normal speed (the idea is to count two seconds).
If you’ve passed that same fixed object before you’ve finished your second “Kangaroo”, then you’re too close to come to a stop without hitting the car in front if it suddenly comes to a screeching halt.
These sudden screeching halts can happen quite often on the freeway in these parts and usually result in a domino effect which makes it very difficult for those at the back of the line to come to a stop quickly enough (sometimes leading to a pile-up).
I know. I went down in the wet last year due to merging into an inadequate space while trying to exit the freeway. As soon as I did, some dipstick of a driver somewhere up ahead must have cut dangerously into traffic causing everyone behind to hammer on the anchors, and causing me to slam into the back of the car in front due to inadequate stopping distance between me and the car in front.
$4,500.00 worth of repair bill; fortunately picked-up by my insurance company. That was on a bike that I bought for $6,999 OTD almost two years ago. The stock muffler alone cost $850 and the plastic fairings cost an arm and a leg too. Thankfully, I was unhurt apart from a dinged finger which fortunately didn’t break. All the gear all the time (ATGATT) folks.
Anyway, if you ever find yourself in a situation like that (sometimes you have to go into whatever gap is available if you want to exit the freeway, or else you’ll miss your turn-off), then you should try to swerve into the emergency lane or the space in between the cars (the white line area), where you just might avoid a collision.
Another good idea on the freeway is to frequently look far ahead up the roads (~12 seconds ahead I believe is the recommendation) so that you might be fore-warned of impending danger.
I hate to sound all doom and gloom, but if you’re sensible, freeways (and motorcycling in general) aren’t such a big deal. If you aren’t sensible, then you could die or end up permanently disabled.
Better to be one of those slower, safer guys than to be a dead motorcycling super hero although being one or the other is a constant psychological struggle for me (but hopefully not the dead part).