Welcome to the forum. As Bob has said, there are a number of members here who should be able to offer helpful suggestions to you. I suspect that you'll find some variety in the responses, which will give you alternatives to consider.
I'm not a deacon and can't really provide you with recommendations for a prayer rule specific to the diaconate, or directed toward formation for it, but I would offer you this, from St Theophan the Recluse, on prayer rules in general:
“It is good to have a prayer rule on account of our weakness, so that on the one hand we do not give in to laziness, and on the other hand we restrain our enthusiasm to its proper measure. The greatest practitioners of prayer kept a prayer rule. They would always begin with established prayers and if, during the course of these, a prayer started on its own, they would put aside the others and pray that prayer. If this is what the great practitioners of prayer did, all the more reason for us to do so. Without established prayers, we would not know how to pray at all. Without them, we would be left entirely without prayer.”
Although not specific to deacons, I might also recommend an an excellent piece on prayer rules
written by a friend.