I do not believe in a personal God. I think any idea of God we...

I do not believe in a personal God. I think any idea of God we have is an illusion. That said imagination is more important than knowledge (Einstein). Prayer and meditation has clear benefits for physical and mental health. Creative thinking is associated with being relaxed, so you may be able to find solutions for your problems by practising prayer. The way to reduce worldliness and emotion is by prayer. If you are calm and relaxed you are less inclined to anger and more inclined to genuine love. It is simply physiology, the way God made us.
We can learn from Saints and anyone with great qualities. What do they have in common. In this instance their habits of prayer.
How to pray, who to pray to. You should pray to who you are most comfortable with, your illusion. You should avoid asking for things for your self (coveting). You shouldnt be bolstering your ego, you should be with out self interest and accepting Gods will. Length of prayer, probably you can learn by trial and error what is best for you. A prayer of over half an hour a day will likely give more physiological benefits than short prayers but short prayers more frequently will help with mental focus. Repetitive prayers probably are a form of meditation. Prayer is addressed to someone, meditation is an exercise, both can have benefits though they may differ in some respects.

In praying and avoiding sin the goal is a mental state that produces behaviour that pleases God and allows us to prosper here on earth.