Creatine is cheap enough that there's not reason not to use it. It's definitely not necessary though. It's also something you don't need to cycle. Take it all year if you'd like. It's not going to make or break you.
It'll definitely add water weight. Anywhere from 2-5 pounds would be normal, although none is definitely possible (and any more than that is probably not from creatine).
Currently, I take:
Creatine
ErgoBolic
White Flood or Fierce Domination, pre-workout
The ErgoBolic is an anti-cortisol, and was almost free due to a bunch of other shit I ordered. I only really tried it because it's supposed to help with sleep. So far, it definitely does, but it's way too expensive just for that. I also use whey powder, but I don't consider that a supplement as much as just an extra meal. Well, two meals.
I'm also going to start taking an Omega-3 since I've had tendonitis and other tendon injuries so much in my lifiting career. I'm hoping that'll help keep them down, but we'll see. I'm currently on an off week after what felt like I almost tore my bicep, which followed another 2 week break back in March when I got what I believe is peroneal tendonitis (deep in my calf). That one actually never went away as I just kept squatting on it, but hopefully it'll be gone after this rest period. I had bicep tendonitis that fucked up my shoulder back in 2010, after which I stopped lifting for a good 6 months. So it's a problem that I'm looking for a solution to. Hopefully Omega-3 is just fucking magic.
Read lots of reviews on the bb.com forums about Fierce Domination that made it sound awesome. Not really a fan. They said it tasted amazing, I think it tastes like crap. And I actually feel like I lose focus after taking it. Mostly on bench press, where I can't find a focus spot on the ceiling and my lift gets all fucked up.
White Flood, on the other hand, I've taken before. I had tried the raspberry flavor back then and liked it. It helped me work harder in the gym. I've got a tub of watermelon right now, and it's by far the best tasting supplement I've ever used (although I did use Green Mag back in the day too, and that shit's delicious). Whether or not the White Flood actually helps, or is just a placebo effect, I don't really care. It gives results, and it's cheap enough for me that it's worthwhile.
If you can't tell, I'm kind of a Controlled Labs fan. Between White Flood, Green Mag, and Pronom 23, they're the best tasting supplements I've ever had. I'm at the point where I give up on other companies because they're always a disappointment, and Controlled Labs seems to be consistently good.