Hi! For me, I would not buy the Lucky Alhambra because of the perceived perception it's hard to get. I would buy it only if you love love love it, and you have had it on your wish list. It doesn't seem that way as you would have already jumped on buying it, so my answer to you is no, don't buy it. Buy only what you really love and want to collect and don't get caught up in hype of something hard to get. Another way to look at it is while it may be hard to get, it is not in high demand as it would have already been sold by now (pre-order, wait list, etc). Also, hard to get does not "not able to purchase with a order." VCA is limiting general stock of pieces that are not super popular, but you can always order them. If you really decide you like Lucky Alhambra later, order it, wait a few months, and poof, it will be yours. For now, I would pass.
For me, I am not a fan of Lucky Alhambra as it is a very different look than classic Alhambra. Lucky is a bit cutesy/childish for me (e.g. heart, butterfly, charm bracelet theme), like wearing a child's theme charm bracelet. I prefer the classic Alhambra line. That's just me of course. Some people prefer the cutesy/childish look.
As for what to get next, I would get either the guilloche earrings to match your bracelet, or get the 5 motif MOP bracelet to match your MOP earrings. I think sets are beautiful. For me, I would get the 5 motif MOP bracelet and wear it together with your guilloche bracelet. You can then wear you MOP earrings with it... so beautiful. These pieces and sets will look so elegant and chic, not cutesy.
Frivole and guilloche... do they match? That is a loaded question and very personal. I will share my thoughts...
At it's core, from a pure design perspective, no, they do not match. If these two designs were no-name pieces at a department store, I don't think people would pair them together as a set. Alhambra is a geometic quatrafoil, while Frivole is a 3-dimensional artistic flowing flower. Very different in my opinion. However, you see it mixed often because people want to bling out in VCA so mentally, "it's VCA, so it must match". If you just want to pile on your VCA, then yes, go for it and put it all on.

There is no right or wrong with wearing jewelry, it's very personal.
Last thoughts... If you have to get something Frivole, if I had a guilloche bracelet and wanted to get Frivole earrings, I would not get the all gold ones. That to me is the worst combination as now it's gold gold gold everywhere with contrasting designs. If you have to wear Frivole with guilloche, I would go with the Frivole diamond pave earrings.
Just my two cents to help you decide. Hope that was helpful. Good luck!