The saying "Its not what you use, its how you use it" truly kicks in this topic.
I know great producers that can achieve a great mix/master on logic using stock plug ins instead of third party plugs. If you're satisfied with your mix, using MB dynamics, compressor, a bit of eq and a limiter should make a nice difference in your final project, just to name a few. Others can argue you don't need much, and its true, but you never want to over do your mix. (*Yes I know, you shouldn't master your own tracks blah blah blah. I can't afford a mastering engineer on all my projects so I do the best I can. I wouldn't even consider them mastered.
Ozone is indeed a great tool to you. A solid all in one mastering plug in if you will. Get familiar with the stock plug ins before you decide to spend a nice amount on Ozone. Its good to know what you're doing. Ozone won't auto-master it for you
Hope this helps bud!