I think some great posts have already been made, but let me add my two cents as I am discerning the calling to be a deacon myself. My interest into this started about ten years ago. Currently, I am waiting to see if I am accepted into the aspirancy program that will start this fall.
Some of the things I will echo is this. Give yourself to helping the disadvantaged and the marginalized. You can do this by helping at homeless shelters, soup kitchens, jail ministry, visit the sick in the hospital or the aging in nursing home, and other things like this. If you do decide that you want to be a deacon and take that first step, the vocational director will want to see what you have been doing to emulate the life of a deacon. Much of what a deacon does most don’t see because he is doing it outside of the mass. Find a deacon mentor who might help you see what it is they do. In fact, find see if you can shadow a few as they will all have different callings.
Get a spiritual director as he can help you transcend some of these thoughts you are having and find out what your motivation is. Is it a calling from God or is it something else.
Maybe as opposed to getting a theology degree, how about taking some scripture classes? That is the one thing that I wish I would have done as if I am accepted into aspirancy, it would be nice to have a leg up on some of that. My spiritual director and I have talked about this, but it was really too late for me to do anything about it. The last scripture classes I had were in high school, so that was some time ago.
I don’t know what your prayer life is like, but deepen it if you can. I pray Lauds and Vespers each day and I also look at the Sunday reading and gospel and write what that means to me personally. I keep this in a journal and it has been a blessing.
Anyhow, I will pray for you and I hope you will do the same for me. Enjoy where the journey takes you and trust in God.