PROPERLY installed gutters would probably be a big help especially if the downspout is pointed away from the garage.
It's really hard to say without seeing pic. what your situation is BUT given that there are no gutters that is where I'd start.

I agree with Carol, guttering is where I would start,too. The only caveat would be if the ground immediately outside where the leak is slopes directly uphill from the building. In that case changing the surface drainage might be a better quick fix.

Assuming it's level or sloping away, then go for gutters. You may need gutters not only on the garage eaves, but also gutters on adjacent structure(s) if they are dumping water down on the ground by the garage's seeping wall.

Sealing from the outside is another task, but sometimes you can get away with just installing some more effective subsurface drains, i.e. french drains, which are not usually too complicated to create, providing you have a suitable outlet for them.

HTH,

Molly~