Look blog commenting only provides link juice to your website and the links are no follow. SO, it is better to generate a good comment on relevant sites in order to increase the traffic on your website.
Simply the black hat SEO is the SEO which does not work under the Google guidance and rules and white hat SEO simply is the proper optimization of your website with proper techniques that Google allows.
Your content should be of almost 1000 words. Do switch to HTTPS now because it is mandatory now. Check your website whether it is mobile friendly or not. Focus on LSI keywords.
Link juice we simply get from no follow links. Google webmaster don't recognize these links only some of the visitors may click on that link and they will pass link juice to your website.
Infographics simply are the graphical representation of your information. Simply after creating Infographics you can post your infographics to different infographics websites to gain dofollow links
First of all remember content is the king of SEO. If your on page optimization is good with the content then there's hardly any need for off page optimization.
Do follow links are basically the links that matters for Google web crawler and helps to reach to your website. While no follow links only passes link juice to the website. If some user click on that link of your's then only traffic can be passed to your website otherwise crawler will not notice...