Newbie, Support hero help.

I believe the support heroes chosen are based on trends, the current meta is a push meta I believe so the support chosen are mainly the ones that can push towers down quickly e.g. Leshrac with his diabolic edict, Chen with his creeps (then again Chen is just plain awesome especially with his mid game heal and test of faith not to mention his creeps), Shadow Shaman with his wards, Dark Seer because of his ability to offlane well and perhaps his vacuum into someones AOE ability, Naga Siren with her song to easy position her team in a team fight or used as an escape.

So you will probably not see some heroes chosen a lot that lack pushing power e.g. Lich doesn't have many skills that can push well frost nova just slows and does a bit of damage and you wouldn't want to use chain frost on just creeps unless you a purge or just flash farming.

The heroes tend to be fairly balanced but different combination of heroes can lead to a better game as their skills work together for example Crystal Maiden might frost bite someone then you might get a Juggernaut to blade fury the person.
Naga Siren ult to get a Dark Seer and a Enigma into position, Dark Seer then vacuums the enemy team together then Enigma uses black hole on their entire team.
Chen uses test of faith on Pudge then Pudge hooks someone.
Some examples of reasons why people pick particular heroes.

This is slightly outdated but I think it is still valid for the most part http://www.dotafire.com/dota-2/guide/picking-the-right-support-5231

tl;dr;
I believe heroes a chosen based on a specific trend along with how the heroes ability work with other heroes.

*EDIT*
Also with the heroes chosen in pro games/ captains mode, there tends to be a lot of counter picking which will affect which heroes might be taken e.g. if one team chose a Chen they other team might get an Enchantress or a Doom Bringer to counter him as they both have something that would make Chen's life a bit difficult. Enchantress could steal Chen's creeps to use against him while Doom Bringer would just eat Chen's creeps. If Doom Bringer was chosen then your team would have to pick someone to counter him perhaps Silencer with his global silence ability to stop Doom Bringer's effectiveness in combat.

This is just an example and might not be a good way to counter these heroes.

I find in a lot of pubs that I play, my team mates tend to pick heroes without a lot of CC or initiation techniques so from my experience I would probably advise you to chose a couple of heroes that you like that has some decent CC or some sort of initiation. Perhaps Tidehunter he has a slow and a large scale disable or Lion 2 disables and a nuke.

Yeah, at the moment you probably want to get max 3-4 heroes together that you can get comfortable playing and that you like. I'd suggest picking some fairly straightforward heroes with easy skills to land - this means you can be immediately useful to your team with fairly minimal game experience. You can concentrate on learning the basics then, before moving up to more complicated/difficult heroes and powers.

Don't worry too much about the current pro-game meta - all heroes are playable and useful in pubs, and pro-games obviously have a very high element of skill/co-ordination that makes certain heroes much more desirable (e.g. it's a bit different playing Io when Dendi is your Pudge compared to some random pubber). Also, the meta is always changing - Lich was in favour for a long time due to his great harassment and lane control. The hero hasn't actually changed, it's just that teams at the moment favour tri-lanes and some push heavy strats, neither of which suits Lich. Most pubs aren't played like this.

For starter support heroes I'd recommend some of the following:

Lion - nice straightforward powers that are effective and fun to use. Reasonable attack animation and can get mana back without needing items. Good ganker, flexible laner.

Lich - a bit harder to use than Lion, with less ganking power, but better team fight ability. Again can get mana back easily, Chain Frost is a bit tricker to get right.

Tidehunter - big tough tanky hero with good kill potential and a great teamfight ability that's easy to learn. Melee so harder to lane with, but lots of fun to use.

Warlock - powers are less obvious in their effect, but a great lane support and team fighter. Tough enough to allow a mistake or two.

Ogre Magi - great nuking combo and lots of fun to play. Melee so more difficult to lane, but again pretty tough and not too tricky to use.

Generally I'd avoid any hero that requires lots of micro-management, specialist equipment or has powers that are difficult to land or possibly counter-productive (i.e. they can go bad and impede your team). You might even want to have a go with the likes of Crystal Maiden or Lina, but bear in mind that your positioning has to be very good with these heroes or you'll get punished.

Hope this helps.

thanks for the input! I think you right about the pro meta and how heroes are chosen. the heroes I love and want to get good at tho are Keeper of the light, Crystal Maiden, Rubrick (once I learn the game more) and Vengeful Spirit.

Good mix I feel and a great base but I LOVE!! Keeper of the light, not that I'm pro but if I had too pick one signature hero it would be kotl without thinking twice, probably going to be my most played hero.