What should catechumens focus on?

Basically three things. First, prayer: developing a daily prayer rule of morning and evening prayers. Second, fasting: following the church calendar and fasting along with your parish. If you have an autoimmune disease, an allergy, or another serious factor, you talk to your priest about how you're supposed to fast, but that's the exception. If you're in good health and not nursing, pregnant, or elderly, you fast like the rest of us, which is basically a vegan diet for about half the year.

Third, you read and study, not to become some theologian. People get this backwards and think they need a PhD in Orthodox theology. It is a basic understanding of the Holy Trinity, the theology of the sacraments, and the heresies that have plagued the church. Everything you really need to know is covered in the Nicene Creed, though each line requires study before Holy Baptism.

The process usually takes about a year, as long as you're living the life and practicing the Orthodox faith in your day-to-day living.