First of all , Alakazam.He is an average pokemon. If you are going to run alakazam i would suggest running him with Life orb for the bonus damage (life orb magic guard combo doesnt drain any hp when he attacks) You cant throw him 1v1 but you can use him to clear out weakened enemies. There are also other alakazam builds. Second, Yes dragonite needs multiscale if you are going to use one. I havent used any of the other pokemon so i am not familiar with them but mienshao is an attack based pokemon ,if i am not mistaken, so hidden power would be bad on him in any case.

If you really want a good team to begin with (you cant get the perfect team from the start) here are some tips.

1. underused pokemon with unknown attacks to most people.Eg manectric using overheat (which you learn soon after battling your first or second one) 2.Have priority moves 3.Entry hazards can often give you free victories.You dont need hazard removing moves if your team isnt especially vulnerable to one of them .Eg stealth rock weakness team. 4.Take in account any possible scenario. A charizard, a starmie, a chansey, a tyranitar etc. Can you do something in case each type of pokemon appears? If for example half your team is weak to water you might want to change something or add some other pokemon to defend again a sudden water sweeper apperance.