What kind of farming should I start?

If I understand the difference between E1 and E2 correctly, I think E2 is a better route for you, if your field is agriculture. The reason is that prices for good quality farmland, even before you buy seed or stock and equipment, is high in the U.S. It would be hard for you to get a profitable farm going. However, if you invest capital in a farmer who already has a thriving operation but wants to expand, you can invest almost any amount you happen to have.

I would suggest starting off by contact the Farm Bureau in an area where they do a type of farming you are already familiar with. If you have raised cattle before, choose a place with many beef or dairy farms. If you've raised grain, look for a part of the U.S. where wheat or corn (maize) is commonly grown. And so on. (You can probably find a lot of this information just using Google.) When you have found a few likely areas of the U.S., contact the local Farm Bureau in each area and let them know you are interested in investing in a farm. Try to find a farmer who, for example, wants to get a new irrigation system but needs capital to do so, and see if you can work out a deal that will be profitable to both of you and will be a better deal for the farmer than he can get at a local bank or credit union, perhaps on the basis of a share of the crop for a certain number of seasons rather than interest payments in cash. A farmer whose land is good but whose credit is bad may be willing to do business with you, and I believe this would help you qualify for an E2 visa.

I have another reason, as an American, for suggesting this instead of trying to buy a farm: Even if the capital you have were enough to start a profitable farm from scratch (which it isn't), America has more than enough American farmers; we don't need to "import" any of those. We have farmers struggling to save farms that have been in their families for generations, and if you can invest in them, that is better than coming here and replacing them.

It's not quite as easy as showing up with money and an idea. Do some research on the immigration process as well. $100K is really not enough to start a sustainable farm in most places - the land itself would run a lot more than that. Randomly picking Iowa as a starting point:

http://www.landsofiowa.com/iowa/

There are a few places you can get land for $100K or less, but you haven't started any farm yet.

like all new businesses, you need to do market research and

write a biz plan.

I suggest you seriously consider being a partner in an LLC

of a farm that is hurting that you can fix.

can guide further