Cool guide, I've playing support Taliyah lately and I must say: I love it hehe *w*. You should think about adding some bbcode/banners so that you can make your guide's look more appealing! And I agree, you should buy Ionian Boots of Lucidity when playing Taliyah supp :) It has a lot of potential if you work on it... i'll give you your first upvote ♥ GL!

Overall pretty solid guide. To add my two cents, I think lucidity boots are easily the best choice on Taliyah, to be effective she can't afford to spend much on CDR, and adding a bit of magic penetration adds very little to her damage output. With defensive boots, that's really nowhere near enough effective defense to save you, if you misposition on her you're just going to die.

She's quite effective in lane with conservative positioning and safe poking, but falls off very hard until you get your Rylai's when she becomes very effective again. In my opinion, the best way to build her is to grab Frostfang, CDR boots, and sightstone, then immediately rush Rylai's so that you're not so weak in the midgame. Then, once you complete Liandry's, you're cc'ing opponents very effectively and doing excellent DoT damage to them (which again, magic pen will barely add to).

The path to making her effective as a support allows for almost no variation, because if you don't have a slow on your Q you're contributing significantly less than basically any other support. She can't afford significant resistances, CDR, or AP until she at least has that rod. After that and your Liandry, it's typically more effective to add some resistances or utility (e.g. Banner/Zz'rot/situational response if you're getting assassinated) than to go for even more damage. You'll probably be doing the second or third most damage on the team with just your Rylai/Liandry while providing near-constant CC, you don't need to outdamage your carries. She's most effective grouped with, and protecting, the ADC together you can melt any threats very rapidly.