Rosin is key in getting a good bowed sound, so don't cheap out on this key ingredient to success, it can last a long time - and isn't very expensive. In fact, some bassists carry two or three different cakes just in case the environment makes another consistency better for that particular situation. When the humidity is high, the more powdery, harder rosin is usually best, and during very dry periods some stickier stuff may be needed.
Pops rosin is a very popular choice, it leans towards sticky. It is good for students and professionals alike. It comes in a convenient plastic cup with a sealing lid. You definitely don't need much, just a little dab (a couple swipes) will do ya.
Softer rosins like Pops are handy to have for when your playing environment is cold and/or dry, when a harder rosin just isn't "grabbing" enough. Here, in the humid Northeast coastal area that is Southern New Jersey, Pops can tend to be a bit goopy, especially in the hot, muggy summertime. Personally, I prefer something a bit "harder" in consistency, like the Carlsson Swedish rosin. but like anything else, it's up to you, the player, to find out what works best for you. With Pops, having FRESH cakes is definitely key; it does tend to get stale - reducing its effectiveness - when exposed to air, so it is important to seal the cap on the (included) airtight container when not in use -- your rosin will last a lot longer!
New players: I include my personal notes on care and usage of rosin.