I’m going to speak from how I did back in the days.
More meditation! I didn’t meditate often at all because I found it boring (sadly, I was lacking understanding of how important it was and is to meditate) and meditating before invoking any spirit.
Another thing I wish I could do is to never doubt myself, if I was good enough to succeed or not… I was pretty insecure back then and I didn’t know that even if you don’t get huge signs of it’s presence doesn’t mean that the spirit isn’t there because it is.
And of course, I used to cast a circle of protection which isn’t necessary, I should have casted a circle to balance the energies instead.
What you should do is as you said, meditation and developing focus skills because it used to be difficult for me since I was lacking concentration and focus generally. Learn as much as you can about the spirit you’re wishing to invoke or evoke, Offer the spirit something it likes, it can never go wrong with that it’s like you’re inviting a new friend over to your place and of course you offer your new friend something it likes, but I wouldn’t offer blood until the point you two are closer to each other because it’s one of the best things you can offer at least from my perspective. Don’t cleanse the area after the ritual, it can be pretty nice to still have the energy being in the area at least that’s for me. I always shower before invoking/evoking a spirit, it feels pretty great and to shower makes you relaxed. Learn to charge sigils, I found it more easier to contact the spirit afterwards with a charged sigil (doesn’t necessarily mean that it’s going to be more difficult without a charged sigil).
Try the blue ray meditation, it’s really helpful to silence your mind, to stop being a slave of your own mind.