Thing to remember about talents for supports is in a lot of games you're not getting the last, or even the 2nd to last one. They haven't changed that much about support xp that I can see, and it looks like they actually nerfed pulling with the way the new jungle works(just going off the notes, haven't tested, but 2mins creep spawns obviously means less pulls). Some of the supports have % xp low tier, but even the lowest tier is still lvl 10, which sometimes for supports will take 15mins to get to, so you already spent a good amount of the game not having the bonus. The xp is rescaled, but not in a massive amount that we'll see everyone reach last level like you see in LoL a lot more often, it said lvl 25 is now the equivalent of previous lvl 23, and honestly if I were to go and check how many games I reached 23 as a support, I doubt it'd be more than 5% of my games(unless midas).
And on newbie issues, both talents lines seem very strong in pretty much every case. So even if you pick randomly, you don't end up with like a major downside or whatever, they're not gain x lose y talents. After that, you mostly pick what makes sense for you in your game, and that should be fairly obvious. Dying a lot? Get some defensive stats. Support? Get the xp/gold gain stuff so you scale better. Only the lvl 25 talent tends to have a major impact on specific skills but most of them are still good regardless.
One of the best things for supports though: 3more inventory slots to put shitty wards and smokes in.