My first espresso machine! Advice? [Breville Barista Express]

I’m new to coffee and bought my first espresso machine! The Breville Barista Express. I’ve been experimenting with it over the past couple days and can’t seem to get my shot right. The closest I’ve gotten so far is using 20g Starbucks dark roast espresso beans and grinding it to a size 5. I don’t plan on always using Starbucks beans, I just bought them to experiment with. Those who use this machine, what types/brands of beans and grind size have you found works best for you? Any special tools or techniques I should use? I need ALL the dialing in help for this machine to get those perfect pulls! Thanks!

I’m new to coffee and bought my first espresso machine! The Breville Barista Express. I’ve been experimenting with it over the past couple days and can’t seem to get my shot right. The closest I’ve gotten so far is using 20g Starbucks dark roast espresso beans and grinding it to a size 5. I don’t plan on always using Starbucks beans, I just bought them to experiment with. Those who use this machine, what types/brands of beans and grind size have you found works best for you? Any special tools or techniques I should use? I need ALL the dialing in help for this machine to get those perfect pulls! Thanks!