dcumpian
I'd recommend using only what comes with Sonar until such time as you find yourself limited by them. Unless you are a superb mix engineer, it'll take several years before you have learned enough to try a technique that the supplied plugins cannot do.
I completely agree with this. The Sonitus bundle is long in the tooth but still a solid workhorse and, if you are new, a great way to learn since the controls are pretty straightforward compared to some "vintage" style plug-ins. The Nomad Factory plug-ins add some nice variety and character. The remainder of the included VSTs, the ProChannel and also the included virtual instruments are all nice as well. There is more than enough to keep you busy for a long long time.
The plug-in world can quickly become an endless pit of time and money. Finding, reading about, downloading, installing, evaluating, buying, shopping for deals, dealing with licensing, learning, mastering, reinstalling/re-licensing/re-scanning because stuff broke, blah blah blah. It can be fun and there are lots of great plug-ins out there but I'd advise avoiding it for as long as you can.
If you do get bored with the built-in ones and feel like exploring, there are freebies from Melda, GVST, Voxengo, Blue Cats, etc. that are excellent and fill in some gaps and are mainstays for a lot of us even if we do have a ton of paid plug-ins as well.