I form a tribe and become king and after the season they come saying i didnt keep my promises and angered ancestors and always want me to step down everytime.

Maybe you tried to form a tribe too big, and had to accept too many compromises as a result? Trying to go over 5 clans can be seriously unwieldy. Or are they arguing about the promises you made to become king?

I don't remember angry ancestors bitching about my tribe, but I had some promises seriously bite me in the butt afterward. Most of the promises you can make during clanmaking seem innocuous enough, or even good ideas (like litteracy for tribe kings), but they generally have a nasty side effect.

My tribe had 5 clans in it, and also the promises u make like sacrifice 20 goods or buy pots, is it auto done or do u have to manually sacrifice and send wealth?

The really specific ones (buy pots, build a tavern, litterate chieftains...) are more or less automated, and the crisis they might generate will be tied to specific events. For the sacrifices (or the promise to attack/not attack somebody?), I don't remember if it's automated (it's been a few years since my last playthrough)

Note : You may also have a simple political problem, though. The "you angered the ancestors" sounds like something a political rival inside your own clan might say to discredit the chieftain during a power-grab.
You said you were just elected as king. Did you perchance chose a young inexperienced noble to be your chieftain, hoping he would have a long reign and get better? Maybe you have an older noble with a high Leadership stat in your clan who would want to become clan chieftain? Or, if it's the Tribal King title which is challenged, maybe another clan's candidate is a sore loser and tries to force you to step down?

The way you describe this, it really sounds like a plot from political enemies against a weak chief/king.

Tribal agreements are handled automatically (other than a few that should be obvious, like promising to elect queens).

It seems that you do. :)