I have a terrible support pool and I don't enjoy playing support. When I play ranked teams, I am usually slotted into the support spot and play alistar but find him boring. Which Support should I buy now? I was thinking Braum, Thresh, Blitzcrank, Leona, Nautilus. Please help and give me your thoughts :).
Leona. I always like her as a support no matter what ADC I am. Also, you won't get flamed for missing your grabs/hooks.
Blitzcrank is probably the safest, easiest, and most able to make simple plays. If you don't intend on putting a lot of effort into it, that's probably a good choice. He's not the best in all those categories, but he's quite good in each. Leona probably stronger though, with Thresh being the top tier pick but has a higher skill floor.
Depends on what your play style is.
Tanky: 
Ap damage/play makers:
Passive/utility:
for tanky supports, i personally prefer thresh because even though he can be hard he has a generally safe early game and can easily snowball games with amazing plays when you master him
leona is also a great choice and the damage she can put out in a trade because of her passive is amazing, you rely entirely on your adc following up though(unless your really far ahead or the enemy is really bad) but i guess you dont have to worry about that in team ranked. she can also be very hard when behind though because of how aggressive she needs to be which is why i generally prefer thresh
you might also want to consider nami and vel koz though, both are also amazing supports when played correctly
