Also you can buy it via steam or FFXIV outside of steam

Also you can buy it via steam or outside of steam, if you do buy from steam you have to buy expansions through steam and if you buy outside steam you have to buy outside of steam. It's cheaper to get it outside steam since you get better deals, it doesnt matter which you get as they are the same content and game.
You can add the non steam FFXIV into your steam library as an 'add non-steam game' to library list.

I started 2 weeks ago, and have had a great experience so far. New players like myself have a little seedling symbol next to their names, and I see so many of them around. It's easy enough to find groups or queue for dungeons at low levels. I think the recent sales on Steam and PSN have really boosted what is already a very popular game and added lots of new players. I would heavily recommend the game too. It's a cut above most, if not all, MMOs in my opinion.

I came back about six months ago after not playing since pretty much launch and it was wonderful. I didn't feel like I was at a disadvantage at all, and actually after the most recent patch dropped I actually RESTARTED because they added some really interesting new quest icons to show you what quests will unlock things, etc. It made leveling for a second time even better!

You're at a disadvantage in that you have to level to cap, gear up and will be lacking all event rewards that occurred prior to your starting.

That said, you can still catch up and be "on par" with others in Buy FFXIV Gil terms of gear and skill. The game itself is enjoyable and missing out on previous events is not going to change the game from good to terrible.

It's never too late! As cheesy as that sounds, if you actually sink a decent amount of time into the game (i.e. Not just play a couple days a week for a couple hours) you can make big strides to reach "end-game" status and start taking advantage of the weekly lockout stuff, and be caught up before you know it. It's more about putting yourself in a position to be ready for the next big patch, which is a lot of work, but definitely in reach.

I picked the game up on Black Friday (got a great deal on the PS4 ARR & HW pack). I got caught up on MSQ two days ago. It's been one of the most rewarding experiences in gaming for me. I love the community and their enthusiasm.

My biggest problem was that I got side-tracked very easily. Started as a PLD tank...and then thought "Wow, WHM looks cool!" So I started playing other classes for weeks on end before going back to the MSQ. It's so easy to get wrapped up in other class systems, jobs, etc. I don't have much MMO experience, but I'm hoping this game lasts for quite awhile.