Let's also look at the Fumbi shop and Enchanting.
The fumbi shop is random shop essentially. You spend pen to gamble on a random drop, whether it be a clothing piece, weapon or something from the coupon shop. It is all luck based and mostly you will get a temporary item that can last either 1/15/30 days(I might be wrong on the day duration, there might also be 3 or 7 day duration as well).
Now is this worth the pen? It can be, when I start new characters sometimes I will try my luck on each piece of clothing and use that clothing til it runs out and try again. There is always a chance you'll get a perm and then you won't have to keep spending for that piece of clothing or weapon. Alternatively you can just keep buying clothes/weapons from the actual Pen Shop, you'll make your pen back playing matches and ranking up gives Pen as well. It's really up to the person if it's worth it or not. The Fumbi shop has clothing that isn't available in the Pen Shop so it might be worth it for style or get a certain weapon skin. Just don't go overboard gambling and then not have any pen left. The Coupon shop is where you'll be spending, you guessed it, coupons. Coupons come from capsules when you don't get perm items, so they tend to stack up over time. The coupon shop spends 50 coupons per spin. I've been hoarding mine on my main account because I have hopes that they'll change the coupon shop some day and make the rewards worth it to try my luck. It's up to the person if the shop is worth it or not, you can get capsules from this shop but it's all about luck. I won't be spending mine til they take the esper chip capsules out of the coupon shop as they are kinda useless, you only get temporary esper chips from the caps.
Next let's look at Enchanting, Dismantling and Item crafting.
You might have items in your inventory that have day duration that you simply don't want anymore and they're taking up space. Well now with Dismantling you can take apart timed items. You have to press the '-' icon on clothing and weapons that have at least 10 days worth of time left on them. Then in the chat box infront of the text "days to dismantle(min.: 10) you can type how many days you want to take off the item. Example above, taking 10 days off a 30 day shirt or 30 day skirt. Clothing yields 1x of gears you get from dismantling where as weapons yield 3x gears. These gears can then be used towards item crafting. It can be a very lengthy process and some don't think it's even worth it to do it but I leave that up to the person. For a more in depth guide, the wiki has more answers
http://s4league.wikia.com/wiki/Item_Crafting_System Sorry for not going over it, I'm lazy.
Now Enchanting is another thing that's optional, over time using your weapons and clothing in matches you'll build up a bar on them with MP(Please don't ask what MP stands for, I'm too dumb to know, too lazy to look it up). Whenever the MP bar is full you can then enchant your weapon, it's random what bonus you'll get. Enchant examples are +1% defense piercing, +1% Touchdown Defense etc etc. It's usually a waste of Pen and time to enchant anything that isn't Perm unless that item has a ridiculous amount of time on it, something like 377 days on a sigma blade or 545 days on submachine guns.
And last but not least, Esper Chips and Chip enchanting. Esper chips are things you can put into Weapons and Clothing, only a few can be put into Pets. Esper chips will mainly be attainable from the Cash Shop/Tiered Spender for people who drop money on this game. You can get temp esper chips from the Coupon Shop or from Daily Missions. Some are worth using for a couple of days like +2% attack for Weapons or +3% Defense on Pants etc. But the ones you should hold onto are the ones you get from logging into S4 daily, they can look like this
These chips are perm and you can enchant them up to lv/rank 4, every time you enchant them to a higher rank their bonus gets better but the chance of success gets lower each rank up. Warning: You can also have a chance of them breaking when trying to enchant them. Never put a perm esper chip into a temporary item, when the item's time is up they'll be gone along with the chip. So wait til you have a perm item that you know you'll be keeping/using to put a chip into.