Hydration systems are excellent, and have many recreational uses beyond Airsoft.
I'm glad that you're looking into purchasing one early on. It will save your butt and/or make your game much more comfortable.
As a first purchase, I recommend the Condor Water Hydration Carrier
This system offers a no-frills big dirty pouch for up to a 3L Bladder or the included 2.5L Bladder and a few snacks. It has MOLLE straps all over it which allow you to add extra pouches or flair. You can either use it with the included shoulder straps on it's own or with a Recon-style rig (if you adjust them correctly it is very comfortable), or you can attach it directly to a MOLLE plate carrier.
It's available in standard neutral colours or ATACS/ MULTICAM.
Personal experience: 8/10 would buy again.
Then there's the Hydration Carrier II
It's the same basic idea but with added pockets built in for stuff. A nice option for day-long games without having to haul a 3-day pack or assault pack. Use alone while going for a day-hike or a 40k bike ride, or for your airsoft game. Carry extra STANAG mags for your friends.
Doesn't sit too high while attached to a plate carrier in prone position.
Buy this if you like to carry extra hamburgers not on your tac vest.
These two can be had pretty cheaply within Canada, and afford the best flexibility and build quality within price ranges for airsoft stuff. Any less and you get a shitty bladder or no bladder at all. Any more and you're paying for 1337 operator gear that you probably (definitely) don't need. You can always buy one of these carriers and buy a superior bladder if you so desire, but a fancier carrier will not offer any more utility unless you have a specific need to fill.