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.