HPMA pay to win currency. This is bought in the jewels shop and can be used to buy most other currencies. These are probably the most valuable
Gems
Second most valuable currency. Can also be use to buy most other currencies and cosmetics. These you can earn just by playing the game. I like to ration these and buy bundles here and there.
Gold
Gold is probably the third most valuable currency. It is the only currency you can use to level up your spellbook which makes you stronger.
Keys
More information on the shops guide page
Gold Key
These are used in the Magical Studies section in the Shop. You can get any card in the game through this draw. You are guarunteed a legendary (orange) card every 20 pulls. I do not really think these are worth saving.. Maybe if you really want a chance to get the next banners cards if it is added to the banner? Otherwise I would just use them whenever.
Silver Key
Similar to the gold keys, they are used in the same shop. The only difference is that you can only get up to epic (purple) cards in this. You are guarunteed an epic card every 30 pulls
Ruby Key
These are used to roll on the event banners. The Ron one seems like it is permanent for all players and gives you a discounted roll cost at 9 instead of 10 keys so I would utilize this. Your Ruby keys will NOT expire and can be used in the next event. I would save these until you see an event card you really want.
Clockturn Key
These are used to roll on the Mystery Wheel. These keys do NOT expire and can be used for future wheels. F2P recommendation is to save until you are more or less guarunteed to get all the items on the wheel.
Forest
Echo Crystal
Used to upgrade your echos. Recommended use is NOT to level up echos but to change out the cards that get bonuses.
Leprechaun Gold
Currency earned during your forbidden forest run. Used to upgrade cards at the merchant or abilities in the rest area. These expire at the end of run and do NOT carry over to the next run so use it while you are in the forest.
Thank You Notes
Earned when playing with others in the forbidden forest. Can be used in the Thank You Note Shop. You can farm up to 10 per day. If you miss one day, you can farm up to 5 days worth or 50 thank you notes.
Club
Club Coin
Used to upgrade club abilites in the club adventure. No point in saving I think. Use them immediately. Earned by participating in the club adventure.
Club Crest
Can be used to purchase trade tokens in the card trade shop. Earned by doing club activites.
Trade Token
Used to trade cards. Each token type represents the type of card you can trade between common and legendary cards. You need one to initiate the trade then one to accept a trade. 2 is used per transaction.
Others
Madam VIP Coupon
Used to get discounts at the clothes shop in Diagon Alley. You can earn these by dancing. The gold one gets you discounts on the event exclusive alternative outfits. To buy these you must already have the original event outfit. The purple ones give you a discount on all other items.
Pass Points
Earned by participating in dailies. They level up your magic pass. The top is free while the bottom rewards costs money.