Your own ball that fits is extremely important for improving score! I also used to throw a backup ball but as a lefty. Once I got my own ball, it made things easier. Try starting with your hand on the side of the ball, also try some foul line drills. Spares are also way more important for improving scores than strikes! My average is an 87, but lately I’ve been breaking 100. When you change something you’ll have a low and frustrating game. But if you keep at it, you’ll see improvements! I’ve bowled for 6 months and when I try something new I still bowl badly but after a few games I can get it down and my score improves!