Not smart to try leading a horse over a jump from the ground in-hand if the horse is flighty/bitey/very large/or otherwise runs the risk of you falling under him or getting yanked forward. Deadbrokes and calm ponies can probably be lead over, if they are comfortable being in-hand already.
Straight lines don't put stress on the ligaments like circles do. My mare just got a sore hock from me lunging her more than riding her. If you can, wall off a square or rectangular arena or large paddock in a way so that there are no real corners, set up some panels or even tie a lunge tether TAUT (not tight, straight) from one side of a corner to the other side of that same corner so that your space is shaped like an oval with straight sides but curved ends.
Start small. Very small. ONE pole on the ground. Then another. Until you have a set of trotting poles about 6-8 strides long. Space them correctly; put one pole down on the ground, step in front of it so that your heel touches the pole, then put your other foot directly in front of that foot so that the heel is touching the toe of your foot nearest to the pole, and take another few steps the same way. Trotting stride is usually 4 human footsteps, unless you have large or small feet xD
Put another pole down in front of your toe when you reach 4 steps. So on so forth. When you can get her trotting over poles without a hitch, no problem at all, raise all poles about 4 inches off the ground. The goal here is to muscle up her "carrying" muscles and teach her to regulate stride so she doesn't end up plowing through a jump because she can't space herself. When THAT doesn't have ANY problem at all for at least one week (some horses have a good session one day, and their riders throw a jump at them the next, and are suprised when they fall or freak out), take out the last pole and put a little 12inch stack jump in its place. Horse should trot over and give a little hop. You can use a crossrail, but keep a pole on the ground under it so the horse can judge the depth a bit better. A week later, take out the beginning pole and put a 12in "jump" 6-9 human footsteps ahead of the little stack you already have at the end. Horse should trot over the 4in poles and canter over the 12in stacks. Later you take out all the 4in poles and have three 12in bounces to canter over. Week after that, you stack up the last 12in hop to a height of 16-20 inches. And you can start taking out the other 12in hops or keep them for gridwork. Training a horse to do much of anything is a long and patience-demanding activity, try not to be discouraged or rush the training.