Manual Backlinks - Which Type Worth Spending Time On?

I started learning SEO (again) and I am seeing positive results so far using GSA SER + manually created WEB 2.0 with manually written content + Social Signals on money site and on web 2.0 as well. I want to take things further and create manual backlinks, but I am not sure if this will worth something and which one if so:

1. Q&A websites - finding question related to my niche, create account and answer on them placing my link. Also create 2 accounts on high PR Q&A like yahooanswers and create 2 accounts, one for asking the question and one to answer it using my link.
2. Forum Signature - finding forums related to my niche, create accounts and posting on threads until I have permission to add a signature.
3. Blog Commenting - finding blog posts related to my niche and comment on them using my link. I know there are commenting platforms as Disqus and Livefyre which are not always moderated, but if the blog is not popular where my link can be seen I don't know if will worth something.
4. Social Bookmarks - creating accounts on sites like digg, reddit and add my link wherever I can add one.

What are your thoughts on this ?

PS: I am not ranking a whitehat niche, I am using CPA for monetization.