So mill is my favorite thing in all of Mtg. I have a mill deck that I am very happy with. My recommendations are to not focus on creature power, focus on abilities. Like, I used to run Wright of Precinct Six, but there are so many other things that I think are better (of course, this also depends on what you really want to go for. If you want to do a zombie mill deck, he would fit perfect and would be a must have.) Make a clear definition of what your mill method is and commit to it FULLY (and there are a lot of mill methods), If you're going for damage and mill, as in you're just using your opponents graveyard against them more than actually winning via mill (cuz damage will always kill them first) I would recommend
Mindcrank. I used to run
Mindcrank, but I kept killing with damage and I'd rather mill someone out. And last piece of advice, what really changed my deck and made it a lot stronger, was using almost purely Dimir mill. Like, 95% of the cards in my mill deck are both black and blue and are either from Ravinca or Return to Ravnica blocks. It makes mana distribution a lot easier and mixed color cards tend to be more powerful (i.e.
Mind Sculpt vs.
Glimpse the Unthinkable.) But in the end, don't be afraid to experiment with it and play around. Mill is one of the hardest things to pull off in Magic, but also one of the most rewarding. And if you do it right, it's one of the most difficult strategies to counter. Mill is hardcore.