I've had to adjust a bit of my process now, with how the renting marketplace is going, I went ahead and edited this one before posting to be more user friendly. Unfortunately, with how many users are buying and joining right now, there's not enough cards to go around, and many players are taking advantage of this and buying out all the cards they can find of a single card to force high renting costs. Chicken is a particular example, which used to be just 1 DEC / day...
As such, there are many cards I would genuinely recommend to a beginner, but they're so expensive to buy or rent now that some of them just aren't possible.
About the Earth Splinter
I find Earth Splinter to be very difficult to use without additional cards, as such, I've decided to start with it and Light, which I think are the 'weakest' in terms of your starting cards.
Earth is a very balanced, versatile set, by mastering it, you have a very solid chance against almost any splinter. This is a double edged sword however, as Earth's only really strength is a high health pool for many of its cards.
I will start with 5 core cards. A few of these are absolute MUSTS for Earth Splinter to really work:
#1 Wood Nymph
The #1 Card you need to help out your Earth deck is this card. Earth REALLY benefits from having a healer, and it's one of the only sets that does not have the healer within its starting cards. With 4 Cost, 1 Magic, 1 Speed, 2 Health, and a heal to the first position every turn, this SEVERELY boosts Earth's success rate in all levels. If you get 1 card on this list, I would focus on this one. It helps in low mana, it helps in poison, it helps in earthquake, it helps in high mana with a very high health tank, it helps in armor rounds, it's a really solid card.
At the time of writing, a Regular card will cost you about $2.07, and a Gold Foil will cost you $17.89. For renting, this card only costs 0.1 DEC / Day, making it one of the cheapest cards to rent! This card as a Gold Foil costs about 5 DEC / Day
#2 Centauri Mage
Magic Damage, high health for Wood Nymph to heal off of, AND a reflect on ranged damage makes this card a really solid offensive tank in its own right for high mana battles. She's also very cheap.
Costs: Normal: $0.84, Gold Foil: $17.99
Renting: Normal: 0.1 DEC / Day, Gold Foil: 2 DEC / Day
#3 Nectar Queen
The Nectar Queen is cheap, but honestly, she's a very solid pick for Earth as an alternative main tank to the Mustang. She's better in Earthquake rounds, and has a bit more health than Mustang, more damage, but comes at a slightly higher cost. For me, this and Wood Nymph were the options I needed to start more consistently winning matchups with Earth. She's a really solid tank for a very low cost.
Costs: Normal: $0.50, Gold Foil: $8.90
Renting: Normal: 0.1 DEC / Day, Gold Foil: 1 DEC / Day
#4 Brownie
You're seeing a pattern here: Low Mana cards really help round out teams, and give you WAY more options for Low Mana rounds. This one in particular is basically a direct upgrade to Creeping Ooze, not only does it have the same stats, plus melee damage at the same cost, but it also offers +1 Speed to your cards. You'll likely never use them together, but this little guy gives you slightly more damage and options for Earth. He is EXPENSIVE though for a Gold Foil. As such, I would recommend just snagging a level 1 to bolster your Low Mana battles and buff your other, more important cards.
Costs: Normal: $15, Gold Foil: $900
Renting: Normal: 0.34 DEC / Day, Gold Foil: 30 DEC / Day
#5 Swamp Thing
This guy is like the Priest and Sorcerer in Fire and Death Splinters. If you've used them, you know that they are incredible. This, along with them, gains either 1 Range or 1 Magic at Level 3, and the -1 HP debuff is a HUGE deal in Equalizer Rounds, Opportunity rounds, and Earthquake/Poison rounds. I just realized I don't have one of these rented myself and need to rent one as well.
Costs: Normal: $55, Gold Foil: $300
Renting: Normal: 0.23 DEC / Day, Gold Foil: 24 DEC / Day
Summoners
So, per usual, these are recommendations for summoners that a newbie can afford to rent/buy, so I'm skipping legendaries, etc.
Mylor Crowling
This is all you need in Earth as a Newcomer. Seriously. Thorns is situational, but a HUGELY powerful ability that wins Melee Only fights, trumps the entire Fire Splinter, and is VERY powerful in Bronze-Silver. There's absolutely no question here, this one will help you the most with Earth Splinter. It's no Legendary, but it's affordable and very powerful despite that. Since you start with a Wizard of Eastwood and Lyanna, you don't really need anything else as a Bronze player. Although nowadays you might need a bit more to fight in Silver.
This is the most expensive thing I am recommending on this list for a reason: She's good, pair her with Swamp Thing, Wood Nymph, and Nectar Queen on your team and you're going to drop any melee team you face.
Costs: Normal: $8.88, Gold Foil: $60
Renting: Normal: 9 DEC / Day, Gold Foil: 85 DEC / Day
Splinterlands, How to Sign Up
Never played? Interested in getting in on the action? Want to find out what all the fuss is about for these battles, or maybe you've seen a bunch about SPS? Join here https://splinterlands.com?ref=jakkal You can play the game 100% for free initially, without earning currency. If you like it, you pay $10 to get in on the action by buying a Spellbook! You'll make that 10 dollars back in less than a month at current prices. If you sign up, feel free to message or comment and I might hook you up with some free starting cards, or delegate a card to you for a week!