if you wanna avoid looking scared, buy in with no less than 75% of the max. maybe closer to 80%.

keep in mind, there are other reasons to buy in with the max, other than not getting pushed around. you want to have enough muscle to push other people around when you catch a good but vulnerable hand. say TPTK with a 2-flush showing. if you move all-in with like $5 in a pot of $15, you really won't protect anything. in fact it will look like a desperation move.

i know people who intentionally buy in with a small amount and camp out for monsters that they can trap with. they make a hand, bet a "timid" amount, then wait for someone to try and bully them out of the pot. they call all-in, double up, then start using their new chip strength to bully others around. this is a legitimate strategy but i think it's probably not meant for the beginners circle.

ChezJ