The reality is, for most sites / niches, you can get away with GSA quality for diversity.
Why dont I use GSA for diversity?
1. Horrible link retention rates
2. Poor Indexing Rates
3. Poor creation of Web 2.0s (hint, dont even bother)
The penalty risk is low. But the fact is your GSA links have little SEO value aside from lowering anchor ratios. And most will not index.
For diversity you want:
1. Most likely to index
2. Most likely to stick long term
You can attempt to force index. A year ago I could force index profile links with about 1,000 blog comments. Now? I need more. Google doesnt index crap as easily. Those blog comments, if indexed, are not likely to index.
With all this in mind, a few link types will index. But only one can guarantee indexing and longevity if not horrible quality.
Parasites.
Any link type people use as a parasite will index and is optimal. Youtube, weebly, wordpress, imugr are just some examples of what will always index.
Look up parasites and build those links as diversity.
The common link types which index and stick are:
1. Image links
2. Google Properties
3. Web 2.0s (as long as decent quality)
4. Profiles
5. Doc sharing (dont share junk)
I can keep going, but you get the gist.
GSA isnt bad. It is just that you can guarantee results with other links. Most people, if they get manually reviewed, will fail either way.
You goal is to build links to prevent a manual review and still rank. To do both you need links that stick. Stick rate has a lot to do with quality.
The cheats are images, videos, and very well spun content (which is manually edited to read well).