Hi there! First off I would like to start by saying I am a single Christian who has never been in a relationship other than the one with God. I am curious, how in your marriage have you kept your relationship in God strong while also working on your spouse?
I'm not sure what you mean by "working on your spouse", but I hope you don't mean that you think we should be trying to change our spouses, or viewing them as like, an improvement project lol. Maybe you meant "working on your relationship with your spouse"
If you want a strong relationship with God once you're married, you need to have a strong relationship with God
before you're married. Because you'll be the exact same person before and after the wedding ceremony. The only difference is that after, you'll have a lot more responsibility and a lot more at stake.
Make sure you marry someone who has at least as strong a foundation in faith as yours, if not moreso. You want someone who will match you, and hopefully challenge you, not someone who's going to drag you down spiritually, and have you always trying to bring them up to where you are in your walk with God.
If you're both walking with God before you meet, then your marriage can be truly Christ-centered. And then, once you're married, make sure you make things like prayer time (separate and together), Bible reading, and church attendance, a high priority, just as you would as a single person.