What to buy from event shop

Event shops (by that I mean items in shop that are added with an event available for limited time) are one of the places where you'll get the best of shopping stuff.
Although it could be easy buying something, you might be buying the wrong item. Keep on reading to find out and get the best out of it!

1. Equipments

These are available in all events and they are better than most of the equipments available in the regular shop, so you'll most find most underground camps filled with event equipments rather than regular ones. You should opt for regeneration equipments to buy from event shops in most cases, there is enough storage available with the material carts.

A. Requiring event items

Typically there are 3 kinds of them in both storage and regeneration, they are described below along with when you should buy them.

  • Most powerful

    These require the most event items and you'll be able to buy only one (rarely two) equipments if you opt for this option.
    This option is preferred if you are nearing the end of a region. Because by this time, you have good enough equipment that the least powerful option won't make a lot of improvement. Moreover, as you enter the next region, the more powerful equipments from that region will make the least powerful equipments useless pretty fast.

  • Little powerful

    This is the middle ground option between least and most powerful ones.
    You can go for this option if you're somewhere in the middle of the region you're in. But I personally don't use this option, I'd rather go the most or least powerful ones depending on the situations mentioned in those sections. However if I collect just enough event items (and can't or don't want to collect more) that I can buy this, then I go for this. Suppose I have 40 event items, the least powerful costs 15 and this costs 25, I'd go for one each.

  • Least powerful

    These require the least event items and you'll be able to buy multiple of them, which is the reason considering this is even an option. When you've just entered a new region, you'll face higher cost tiles than you've been used to, you need more energy faster, so opting for this option is good since you'll be able to buy multiple items and each will be a significant improvement to what you have since you're new to the region. Personally I go for this option until I am 40-50% inside the region or have significantly good equipment that this option doesn't offer a significant improvement.

B. Not requiring event items

Some events offer equipments that do not require event items at all (for example Christmas 2019 offered equipment for coins and jewels, Christmas 2015 offered equipment for just coins). All events also offer equipments for gems.

  • Material equipments

    You should definitely buy as much of these as possible (unless it offers a significant improvement to your existing equipments).
    While equipments with just coins is rare to come by, you'll find at least one or two events each year that offer equipments for jewels (amethyst, ruby, topaz, sapphire, diamond). You might not have enough jewels to buy all of them so you'll likely miss some of it, but to get as much as possible, do collect any jewels you find and not skip them.

  • Gem equipments

    All events offer gem equipments but they might not be worth the cost. Gems are a valuable resource and you should spend them wisely, I have explained more on my guide on where to spend gems.
    Most events offer just 1 regeneration and 1 storage equipment for gems which is typically not worth the cost. However some events offer gem equipments that cost more (over 1000 gems) but offer a good value you can use for another 2-3 regions before it becomes obsolete. Although free to play players would find it difficult to save up for multiple of these.

C. Unsegmented event equipments

This is not valid for the new events released after 2017 but you can buy one from shop or they gift one originally released before 2017.
If you're in a lower region like Egypt or Scandinavia, you'll find the equipment useful and maybe even better than what segmented events offer and you should definitely buy it if so. But if you're from a higher region like Greece or New World, you'll most likely not find any equipment of use to you, so you need to opt for buying non-equipment items.

2. Food

Food is something almost all events offer, for both event items and gems. Spending gems for buying food is a big NO but let's talk about buying with event items.

Mostly it is something you dump your remaining event items into after buying equipments, but maybe you shouldn't. Some new events, especially seasonal/occasional ones like Valentine, Easter, Halloween, Christmas are released for free the next year. The event items leftover from this year can be used next year when it's re-released as well, and you can buy more/better equipment with it next year. However if it's a re-released/gifted event, it's probably best to dump the remaining event items after buying equipments into food, unless you plan to buy the event when it's available in shop.

You should also consider using all event items on food instead of equipments if the equipments don't provide a significant improvement over existing equipment. If you love maths, here's some:
Considering egypt region (where food is 100 each per event item). Suppose you have 60 event items and the most powerful equipment also costs 60 items and gives 60 energy/hour. If your worst equipment in camp is already 58 energy/hour, then it's not worth buying a new piece for 2 extra energy/hour. If you buy food, you get 60*100 = 6000 energy. If you go for equipment, 2/hour = 48/day = 1440/month. This way you'll need 4 months to get that same 6000 energy you would get from food (2 months if current lowest regeneration equipment is 56/hour, 1 month if 52/hour). And you might have already entered a new region by this time making that 60/hour equipment obsolete and replacing it.

3. Other items

A. Decorations

All events offer some decoration for event items, but unless you're a fan of decorating, don't buy it since the experience gained from it is not worth at all.

B. Green rings / Jewels / Speed potions

Very few events offer these items, new releases mostly don't. But just in case they offer, I'd go for green rings with remaining items after getting equipment.
Some events that offer these are Wild West (2014), Christmas 2014

Summary

Always buy equipments (especially regeneration) if they are significantly above your current equipments else opt for other items.
Buy ones requiring less materials at the start of region and ones requiring more materials near the end of it.
If they don't provide a significant upgrade, go for food instead.