I wouldn't lunge a horse younger than about 3. Putting a horse to work may help eliminate pushy behaviors, and ground driving is certainly an option for a horse too young to lunge. You can do this in relatively straight lines, and the horse learns about responding to both vocal commands and to rein signals without having you stand by his head. I would start ground driving at about 2, if the horse is mature enough to focus and stay with it. Here's an excellent site with an intro to "long lining":
There are a lot of things that you can do to work on his dominant streak. As someone with a pushy little (large! draft cross) yearling, I certainly sympathize with you.
One of the things my yearly and I are working on is subtle expressions of dominance. There are a few elements of equine body language that are very clear to horses, but less so to people.
One of them is personal space. In a herd situation, the dominant horse is allowed to walk right up to any lower-ranking horse and right into that horse's personal space. A lower-ranking horse, when approaching a higher-ranking horse, must pause and wait for permission to approach (or better yet, wait for the higher ranked horse to approach).
If your gelding walks right up to you without pausing, he is making a clear statement that he thinks he outranks you! If he ever does this, then you should take charge of that situation immediately. As he approaches you, when he's about 5 feet away, stand up tall and hold out a hand to give him pause. Once he pauses, invite him to come to you. You've just taken control. If you can't work out a body language that makes him pause, don't hesitate to carry a whip; just use the whip to keep him from approaching you without permission.
Try to be quick about the whole thing: as soon as he pauses, go ahead and invite him to you. If you wait too long, he may lose interest or may press on towards you without permission. Either way
Another way a horse may do something similar is to walk near you, near enough that a polite person reflexively backs away to clear some space. Don't be polite! HE is certainly not being polite, and to correct his manners, you should stand your ground or even shoo him away. It's okay to be right up next to your horse, but only if it's YOUR idea. Don't let him walk right up to you without pausing, and don't let him move you around.
Horses' lives revolve around their body language, which can be very subtle and hard for people to pick up. The more you successfully "tell" your horse that you outrank him, the more he will believe you.