Sushi and Mining are generally considered the best, and, for one, both corps are earliest. Sushi is map dependent though but great for Space games, as is Mining. I only use corps for Space games anyway, and if non-watery maps or Pangaea I will go State Property instead, which is strong in its own right.
If you are just playing casually, then just have fun with the corps you can get. Put them in your Wall Street Holy city, run Free Market, build Courthouses everywhere. Spread the bad corps (that you can actually found - conflicts) to the AI.