I would wait until you see the drop rate on those lucky boxes. From my experience, it sometimes better to buy off other players at the cheap/rush price than actually opening them, if you have the zeny of course. Last month box was horrible. A lot of trash costumes and the drop rate were horrible on anything decent.
Fire Sale box are usually on sale on an unspecified weekend. The content of the box is usually unknown. Not all fire sale box are worth the price. It's really come down to your market and game knowledge to know what to buy and what not to buy at this point. Sometimes the firesales were only 500KP, and the 9 out of 10 items in there are complete trash.
It's also crucial to know how liquid each items are also. You can have an item worth billions, but it could take you months just to sell it since it's not a very popular item. Heroic Backpacks are generally on sale on those Firesale boxes, and they are usually bang for the buck. HBP also sells really quickly due to high demand from every newer players.
Here is my personaly opinion on this month's lucky box. I would wait for drop rate first, sometimes it does seem like they put the trash item at 50% rate to leech more money from your wallet lol. Though a lot of items do seem to have decent items for zeny if you're hoping for around at 100KP/12-13m later. I am still only 2 months playing this game, so my knowledge can be limited sometimes.
Crown of Deceit -- huge waste of KP, Trash
CD In Mouth -- Decent. Very liquid and can be sold some profit later on 45-60m. Very popular among AGI/auto cast build.
Costume: Jack Castle Bat -- Somewhat break even later on.. Costumes are not really liquid when it comes to zeny.
Costume: Devoted Eyes -- Somewhat break even with some profit. Not very liquid. You can use it for a bit cheaper gamble on Kitcoin enchantment, and hope to get aspd stone (400-500M). Note that you will lose BIG if you get any other stones except the aspd one lol.
Fallen Angel Wings -- You hit the jackpot -- Easily 200-250m few months from now
2000x Prize Medals --Jackpot if you're looking to build several character. 2000 medal will almost instantly get you to lvl 99/70 with BMX3 and Costume Goggle.
6x HE Bubble Gum -- Huge waste of KP, complete Trash.
5x Bloody Dead Branch -- Pretty good deal consider how liquid it is, and the price is usually around 8-8.25m.
There are a lot of decent items here on this month box, but don't expect huge profit unless you hit the jackpot (FAW). It also depends on the drop rate I can't tell you if it's a good deal. Some of these items may flunk in price later, but from my observation so far. Popular / highly liquid items do tend to make good profit a couple months later. I wouldn't burn through all of your KP on this box. Maybe Firesale box could be just as good as last month, despite how everybody was complaining how bad it was.