Reward chart-type ideas for 7 and half year old

[BaronConker]

My son is being very difficult at the moment, with lots of wild, uncontrollable behaviour, temper tantrums, not doing what he's asked at school, and arguing with everyone at home. I have 3 sons and I'm well used to doing reward charts - usually along the lines of 'you'll get a star every day you behave well, and when you get 5 stars you can have a toy/sweet etc'. This time though I think it needs to be more instant - meaning, I want to reward or penalise for each display of positive or negative behaviour. If he stops charging around when asked, instant reward. If he doesn't get dressed after being asked twice, instant penalty.
I was thinking of a jar, to which I add marbles or something, then take them away, and the amount of marbles at the end of each day = an amount of pocket money or sweets, or time on the laptop. Does anyone have any other ideas of more 'grown up' reward systems for this age of child?

Is there something he loves?
My DS loves computer time.

He gets 3 'tokens' every day (each token is 15 mins on the computer) and if he misbehaves and ignores a warning he loses a token.
If he does something really well or is extra well behaved etc he can earn a bonus token

that's a good idea. At the moment I say that every misdemeanour means he loses a minute on the computer, but he doesn't have much understanding of time so a physical token might make it clearer to him. Thanks!

I would worry about the taking away of tokens-doesnt that result in another tantrun?

I always just rewarded good behaviour-that would include responding to instructions when asked to do something, or stopping doing something naughty.

If you said you need to have say 10 tokens each day to get a reward, that usually means they are positively trying to be good so they get a token. Always worked really well with mine when they were going through a "difficult patch"

We used to have a treat box. Basically a box filled with tat and sweets that DS would like (very small things). If he was good he could choose something from the box.