
Deck building is the most fun part of Splinterlands IMO. Just remember that it can also be quite addicting. Be responsible. Never spend money that you are not willing to lose. Also, you can always earn some cards for free by completing Campaign Mode as well as battling in Frontier Mode. Renting cards and renting SPS are also options for playing and earning which require very little investment.
Archons
The most critical part of your deck are your Archons. For a couple reasons:
First, they determine at what level your other monsters are capable of playing at. See the Fire splinter Archon Tarsa below.

Tarsa can be leveled up to eight different levels. You can see at what level each rarity of monster can be played at a particular level. For example, with a Level 1 Tarsa your Common, Rare, Epic, and Legendary monsters will only play at Level 1 even if they are leveled up higher.
Second, archons give powerful affects that can be a major advantage in battles. These include abilities as well as stat buffs and debuffs. In this case, Tarsa increases the health of all the monsters in your lineup by one and increases the attack of any Melee attack monsters you have by one.
Splinters
Strength / Identity
You should try to create a strength / identity for each splinter. Here are some examples. My water splinter is Speed and Opportunity. Meaning it has a lot of fast monsters and opportunity attack monsters. My Earth deck is my best Magic attack splinter. When the game first started, there was so few cards that each splinter could really only have one identity. Today there are enough cards that each splinter can have several strengths / identities.
Neutrals / Dragons
Adding plenty of neutral cards to your deck is a good value. Neutrals can be summoned by archons of any splinter. So a good neutral monster will see plenty of action in battle.
Dragons can be summoned by a Dragon archon and combined with another splinter. So, powerful Dragon monsters can give you the ability to create some very formidable lineups. Adding them to your deck is a good idea.
Skipping one Splinter
In order to save money, you can choose to skip one splinter. Whatever splinter is your least favorite, simply do not buy any cards for that splinter. You can get away with this because the odds of that splinter being the only one for you to choose in a battle is very small.
Variety, Variety, and more Variety
In the early days of the game, there were only a few basic rulesets and matches were small to medium size in mana cost.
Mana
The mana cap for battles has increased over the years to accommodate more powerful monsters as well as to get more exciting complex battles. So you want plenty of low mana monsters as well as high mana ones. Below I have sorted my cards from highest mana to lowest.

You can see that my highest mana card is 14 and that I own 15 cards that are 11 mana or higher.
Restrictive Rulesets
The Splinterlands team is very much a fan of rulesets that restrict the cards that you have available to play. These rulesets include things like 'Even / Odd mana only' or 'Only monsters with 3 or more speed.' Some players have complained about this because it requires them to acquire more and more cards. Personally, I very much enjoy battles with restrictive rulesets. Because they require me to make use of cards and combinations that I otherwise would not have used.
Speed
Monsters speed has been an important part of gameplay since the beginning. Back in 2019, the first tutorial that I read about the game stressed the importance of speed over and over again. And the author of that article was correct. Your deck should contain a variety of fast cards as well as a variety of one and two speed monsters for Reverse Speed ruleset battles.
Conclusion
I hope that you enjoyed my deck building guide and learned from it. Remember to take your time and be patient. Getting the best deals on the card marketplace requires patience and resisting FOMO. Rome was not built in a day nor will your deck be built in a day.
Keep Battling
Header image made using Canva. All other images are screenshots from the Splinterlands website.
If you have not played Splinterlands yet, you can join using my referral link:
https://splinterlands.com/register?ref=ninjamike