How much should I practice and what should I work on?

Frequency beats duration. Three 30-minute sessions a week beats one 3-hour session.

For each session, dry-mount the gun (PCPs and CO2 only - never dry-fire a springer), then shoot 5- or 10-shot groups at a fixed distance with the same pellet. Track group sizes in a log. Work on one variable at a time: hold, breathing, trigger, follow-through. Most progress comes from consistent fundamentals, not new equipment. A target practice session of 30 to 60 well-aimed shots is plenty.