For basic servicing such as cleaning change cassette and jockey wheels. I would recommend:

masterlink/quick link pliers which are sooo much easier than doing it by hand. You should get a quick link if you don’t have one on your chain.
Chain whip
cassette tool – you will need a campagnolo specific one. Get one with a handle as it is easier to use.
Metric allen keys

That should cover the basic stuff. A chain breaker is handy if you are installing new chains yourself.
Maybe a pedal spanner?
these make life easier for installing quick links too
http://www.chainreactioncycles.com/au/en/x-tools-chain-connector-aid/rp-prod10221

With bike tools you do to some extent get what you pay for. I have a mix of Park for the stuff I use all the time) and some other cheaper stuff for bits I use occasionally cone spanners.

however, the cheaper chain breakers and crank pullers do tend to crap themselves.

Check out the Park tools website, they have heaps of instructional videos.