Some of the best free dating sites are OkCupid, Bumble, Plentyoffish.com, Eharmony, Zoosk and Elitesingles.
For Serious Relationships I recommend Match.com
I've found that the dating site Match.com worked great for me and my relationship with my spouse.
I found my spouse who I'm now married too on Match.com and we are so far so happy together.
I've also used farmersonly.com and Silversingles, Eharmony and adultfriendfinder.
All those are good dating sites.
If you look hard enough and speak with the person and get to know the person then it can be easy to find a good spouse and have a serious relationship with them.
Sometimes it takes being on a few different dating websites to find the perfect match for you.
So don't give up if you don't find the perfect match for you on one dating website and sometimes it takes a year or so to find the perfect girlfriend, boyfriend etc.