I don’t know what you should buy with Royal Crystal (Paid Currence), i’m a f2p player in MMORPG’s that avoid spending monthly money and when i spend i buy only cosmetics and not consumables things that can be a waste like mats.
I don’t even buy stuff on Mari’s Shop and use gold in legendary engravings and saved a lot for stronghold decorations and for Artist if she had come this year.
I would recommend you always buy Aura, it’s just too good, our version of the game have the option to buy for 420 Blue Crystal, i think it cost around 4000 gold currently, but likely it’s more cheaper with Royal Crystal, but you need to check on how many Blue Crystal you can buy with Royal Crystal and what is the Aura Price in Royal Crystal, and just calculate what is worth more for you.
I remember seeing a Pack of Blue Crystal of Royal Crystal, i don’t remember if it has some limit like only one time per account, 1 time per month or 1 time weekly, i don’t have the game to check it.
You would have to take a time and see what you want to buy it, if it’s has a option for Royal Crystal, Blue Crystal or Gold, how you can exchange one currency to another and see what you think it’s more worth it.
Edit: the only thing i don’t recommend it to buy card pack in Mari shop, it seems we have the worst version and price of them.
Our version of the game don’t have weekly and monthly mats packs for Royal Crystal, i don’t know if we will ever have it, so you only have the choice to buy it from Mari’s Shop or in the Market, depend if you have patience and which one is worth more, i think currently Mari’s Shop is worth more, you just need to check the currently gold price of 95 Blue Crystal, how many Blue Crystal the item you want cost and how many you get, and check what is their price in gold in the Market in the same quantity.
But all that may create a problem with selling all tradable honor leapstones to get more gold, you need to see if it’s worth sell for gold → buy blue crystal → buy mats in Mari Shop, or if you think it’s better to don’t sell them or part of them and get Gold with Royal Crystal instead.
So you need to see how much you are willing to buy monthly and what you are going to buy and do with the Royal Crystal, i don’t buy it so i’m not sure everything you can do, but you can do this:
-Royal Crystal → buy directly the item you want
-Royal Crystal → buy Blue Crystal pack → buy what you want
-Royal Crystal → Exchange them for gold *→ buy what you want
-Royal Crystal → buy tradable Skins → sell in the market for gold * → buy what you want
*Exchanging Royal Crystal for Gold transform them in Blue Crystal that we buy with gold.
*Selling skins in the market, you need to check Royal Crystal currently gold price in the exchanging, the Royal Crystal price for the skins and for how many gold they are being selled for at the market, new skins are likely give a lot of more gold selling then than exchanging Royal Crystal for gold.
There is many ways you can use them, you need to see what are your options, you may feel a burden in transforming Royal Crystal for Gold in one way or another, so you will need to spend monthly or will feel that you aren’t gaining enough monthly gold, if it will be worth to keep selling tradable honor leapstones instead of using them, etc.
In my case, if i continued playing and was capable of puting some money in the game monthly, i would:
1º Buy the skins i want and may even sell new skins when their gold price is high and buy them when it cheap to use in my character.
2º Buy other cosmetics i want, like pets, mounts, stronghold decorations.
3º: Check the price of the Aura for Royal Crystal and how many Blue Crystal i get on those pack (and if i can continue buying them), to see it would be more worth to buy directly with Royal Crysal or buy the pack and buy with Blue Crystal.
4º If i can continue to buy the Blue Crystal Pack and had some remaining i would buy the Weekly Rapport chest (600 Blue Crystal), that make increasing rapport way faster if you don’t have time to be looking every hour in the lostmerchants.com to see if appeared some legendary rapport.
5º May use the rest in some Solar mats in Mari’s Shop, not sure at all.
I really don’t like to buy consumables stuffs that can go quickly and don’t leave something permanent, so i would buy more permanent stuffs like skins or Aura that is temporary but it’s super good with the extra two bifrost, we have the option to get Aura with Blue Crystal so i would buy using my own gold that i made ingame, but i would have to check the 3º first to see if i would be ok using Royal Crystal instead.