I play alot of blind pick and I am slowly thinking about starting ranked.
I tend to play alot of champs in position I find "fun" but alot of times offbeat choices like Jungle Singed and Support Zilean...even playing Sivir as my main ADC does not seem to agree with the ranked meta and I am getting alot of negative feedback from champ select.

So I need to start picking more "competitive" choices and I want some advice. And I have ~100k IP to spend on champs I have the bulk of runes covered already outside of more specialized choices like an Akali page as I don't own her.

You need to play some normal draft before playing ranked. You need to get used to the pick/counter-pick aspect.

It also might be a good idea to pick one role you prefer or are best at, and practice it more than the others. If you were to make it to the higher tiers (mostly platinum and diamond) alot of the players there "main" a specific role while still practicing the others. for example i main support, with AD carry as my secondary (as they are partner roles), however i still know how to play a few champions in all other roles. this gives you one place you're really strong, but if the team needs it you are still able to play something else