[This is the strategy I adopt, I think Microprose geared the game so you would feel better playing this way. But if it had happened like this in reality America would be a very different kind of country today.]
Once, I tried to change the 'names.txt' and the 'tribes.txt' to put on some more tribes and everything became a mess. The Iroquois looked like the Sioux, and the Cherokee like the Tupi, and so on. But I hope more tribes will be put on in the next version.
[You can change lots of .txt files to alter names and production/buy values but you must be careful as the game is delicately balanced. For example if you could buy an Elder Statesman for 10 gold this would ruin the game. Or if you name more than 8 tribes this will confuse the program. Changing .txt files may or may not be cheating depending on what you do.]
The English are pretty good to play as because you get more crosses which means more colonists, which can come in handy when starting a game.
The French are also pretty good but nothing special, with them the Indians are more peaceful which is a good thing. Anyone who has played Colonization will tell you angry Indians are really annoying [you also get a Hardy Pioneer].
The Spanish are probably the worst people to play as in my opinion, all that you get with them is an attack bonus against the Indians [plus a Veteran Soldier]. Which can be useful if you want to drive your score to zero because every Village you destroy loses you 2-4 points off your total score.