Hello and welcome.
-Which version of OS X?
Unfortunately, Aperture was discontinued when Yosemite was released. The latest version of Photos has some basic editing tools, that seem to work well. Eventually, Apple is going to roll some of Aperture's functionality into Photos.
There are a few third-party apps that are highly regarded:
Pixelmator - $29.99 USD
A
ffinity Photo - $49.99 USD
MacPhun's Tonality CK - $69.99 USD is an awesome app for black & white work. Currently, they are running a special for all of their apps:
Creative Kit XXL - $129 USD
Intensify CK
FX Photo Studio CK
Snapheal CK
Noiseless CK
Tonality CK
Focus CK
Additional third-party apps, presets/filters, guides/ebooks/training videos, etc.
I use all of the software mentioned above and they all have their benefits. I really love MacPhun's suite of apps...they are a great company.
Just more food for thought,
C