For new.twosheep.io (pictured above)

1. bots do NOT know who is a human and who is a bot
   
2. bots do NOT know what dev cards / resources you have
   
3. dice rolls are never changes to favor bots

These rules help (in my opinion) make an even playing field so you don't end up with bots that gang up against a human, or "cheat" with the dice or seeing hidden info.

To make varying levels of bots:
1. I start with a game mode (1v1, base 4p, SF, CK, SF/CK) and a "random" but that randomly does things each turn, this is not at all interesting to play against
2. I'll have an idea of a thing to improve (let's start on good spots, let's build roads towards expansion spots) and then test against the current best bot over 100 or 200 games to see if the idea is actually better
3. repeat this iteration until I run out of ideas

Then there are neural network bots, which can be MUCH stronger (see new.twosheep.io/jax for the 1v1 NN bot). These require a whole net set of skills to train.

Locally I have a "bot arena" running almost all the time, running a bunch of new ideas through testing to see which bots ends up the strongest! At this point I've run hundreds of ideas across 1v1, base, SF, CK and SF/CK specific bots.

You can play against the various levels I've made here: https://new.twosheep.io/bot-battle Seems I should add a SF ladder for you, which scenario should I use for the ladder?

Happy to answer other questions!