In Japanese, when making rules, it is better to use "てくださぃ" or "なさぃ" at the end of a sentence, or to use simplified words directly?

it is more polite to use てくださぃ, please. . .

なさぃ is imperative.

If you personally think it is better to be polite when making rules, otherwise it will make people feel forced to read.

ルールをってくださぃ. Please obey the rules. More tactfully

ルールをりなさぃ. Follow the rules. ) it's like saying from top to bottom that you have to abide by it.

people read in two contexts. See what you need to write, and then choose which statement appropriately.