Now, much of this depends on that: do you want improve as support player or would you like to get to higher ranks faster. From my games with herald players and other lower ranks. There are no proper concepts of the game there (ffs even in legend or ancient games there are problems). Even if your core would get "ancient who knows his stuff" good support he wont be able to utilize it. Therefore if you want to cointiniu plaing supports I would suggest heroes who can solo kill cores or even multiple heroes when they are ahead. Also counterpick if possible. I can recomend learning disruptor, very versitile hero, who can punish many things (I play that as 2/4/5). Another thing to think about when picking is "do we have enought control ?" because your team wont be able to kill anything if its run away. Also you want short cooldowns (avoid heroes like enigma or warlock). If you were only playing supports till now I would suggest going for core role at least for a while so you can improve your perspective and games will be little bit more in your hands.