You get 50% of the value relative to your staked Hive just by upvoting posts within the 24 hour period. The posts don't have to be people you like. Upvoting on posts from people you dislike still gets you the same 50% value in the form of curation rewards. Self voting is increasing that value back on your account because you get 50% and more from the author rewards your post generates, it's one way to maximize return and frowned upon because the predominant reason is just maximizing returns rather than spread the rewards across the people in the ecosystem. You can subscribe to this idea or just go your own way and upvote your stuff but both routes have their own consequences. 

> What if i use 10% to upvote 10 user with 1% each. Then 30% i can use for my own.

At your current staked HP, upvoting 1% doesn't benefit anyone. There's a threshold where only posts with 0.03$ value get a payout and anything below that is dust votes.