Yes, if you have much time and have some idea about how SEO works, you can obviously. But you will need to dedicate much time and have to learn about every aspect of technology.
I would recommend finding and hire SEO Experts for the same who can level up your Website because handling an SEO campaign is a tedious task. At least consulting with some competent Specialists will do some good. Creating relevant content while maintaining HTML to text ratio in itself is a difficult task. SEO Experts are highly professional and have access to all resources required for the job. Hiring the SEO Specialist will make your things real quick and in the budget as well.
Secondly, following spammy practices, can make your Website highly prone to Google Penalty.
SEO is not everybody’s cup of tea. If you want to give a try, then focus on Paid ads promotion before SEO. Working on Google Adwords or ads is far more comfortable, and since the results are instant so it would be better to analyze and rectify things.