Hi, it’s not my first goal, and i actually i can have Great Espresso wtih or without Créma, from my little expérience that depand mostly from the beans and if he’s fresh enough, but i’am sure you can have more infos about what can help to have some more créma (with the right beans 
Thank’s
Well, I guess you want more crema for latte art. (I don’t prefer milk for my coffee and I’m not a professional barista but the ones I spoke tell me crema helps latte art) As I experlenced when you use fresher beans you will get more crema. Also, I don’t know if it is the same for everybody, I like my shots with as less crema as possible.
No, just my ristretto
I like some dark créma, visual first, and the taste if not too much 
I do know darker roasted coffees offer more crema because of the extra CO2 gases being released. However dark roasted just are not something my palette enjoys and can taste pretty murky, and given the current trends in coffee and consumers being more educated, I would stay away from dark roasts.
I think your best bet for enhancing crema is using fresh roasted coffee and really dialing in your espresso. I’m not sure what kind of equipment your working on, but espresso usually tastes it’s best at a 1:1.5 ratio or 1:2 ratio. So if your putting in 18g of roasted coffee you want to extract anywhere from 27g-36g yielded output, in probably 25-35 second time frame for starters. Play around and see what works for you.
Do know that if you want crema for latte art that’s fine, however crema is the most bitter part of your shot given that it is composed of mostly bean fiber and is essentially an emulsification of the coffees oils and CO2 being released from the roasting process. The oils in the coffee repel the water but under high pressure, aka 9bars of atmospheric pressure bond and form the foam like crema. There a few really good articles out there on Perfect Daily Grind and Coffee Geek about the emulsification of crema. I definitely suggest reading up on that if your interested.
Hope this is insightful!
All the best
@the_rogue_barista
Could you share these articles? I’m currently having a lot of problem with my own crema being too bubbly and sticky. It’s a soft (light) roast hitting 9bar pressure at 89 degrees on an expobar/fironzato. I have tested different temperatures but nothing seems to change and I’ve dialled the grinder in perfectly (I even fluctuated it to see if it made a difference to the gassy bubbly crema but no difference). The coffee is always between 6-12 days before I start using it also.
My initial thought is my bar pressure is too high… Ideas?