Hi, Calee!
Glad you like the recipes!
As for making your own combos, just start with a base of one you know you like, and change the fruit or veggie a bit (after a while, I found that I would wake up thinking of combinations, and most of them turned out really well for me!).
Stick with a few ingredients at first : a sweet fruit (frozen banana or mango), some water or ice, some greens (spinach is one of the easiest to disguise). If it tastes a bit too green, add some lemon or lime juice or more banana.
I recommend staying away from grapefruit (that's one that went into the compost for me!). Also, some things like arugula and cilantro are quite strong. Use them sparingly (if you like them).
Remember, you can always add more, but you can take out what you already have in, so start conservatively.