I started playing in August 2021 and have been grinding in Bronze and Silver leagues thru rentals. It was hardly breakeven, but I continued to grind to have a grasp of the rulesets, synergies, and the mind games (e.g. to counter based on history or not).
Quick remarks on these four leagues and how I felt:
- Bronze was the most difficult for me. I usually get tilted climbing up because of frequent fights with bots, who seem to have the best possible decks every time. I must have been that frustrated that my first blogpost was about a bot's Bortus anti-magic deck.
Silver was exciting! You get to play a combination of rulesets and both winning and losing give that sense of confidence that you'll do better next time.
Gold was extremely challenging, and taught me so many lessons that are applicable to lower leagues.
Diamond is.. an abyss. Hahahaha! I'm writing this after just reaching Diamond 3 at 2823 rating, my best so far.
My main take away from my 5-month journey?
We should know and take advantage of our league's Summoner Level Limits.
You can find them by clicking the 'Leagues' button located on the right of your rating.
Here's a table you can refer to.
The general rule is that the level of your summoner can deploy leveled up monsters up to your league's summoner level limits. For example:
League: Bronze
Summoner limits: 3(Common)/2(Rare)/2(Epic)/1(Legendary)
Summoner: Lorna Shine (Rare), Level 2
When using an L2 Lorna Shine, I can deploy monsters within my league's summoner limits.
Sample deck:
- Level 1 Legendary - Kralus
- Level 2 Epic - Djinn Renova
- Level 3 Common - Silvershield Knight
- Level 2 Rare - Celestial Harpy
Other examples:
League: Silver
Summoner limits: 5,4,3,2
Summoner: Delwyn Dragonscale (Common, Level 5)
League: Gold
Summoner limits: 8,6,5,3
Summoner: Yodin Zaku (Legendary, Level 3)
One level difference can make or break your lineup due to improved stats or additional abilities. For example, a Xenith Monk at just Level 2 will have Heal, which is highly useful in Noxious Fumes ruleset.
Difference in rental price is not that huge, too, and it's going to be worth it at the end of the day.
Again, this is the general rule. There are Summoners who do not strictly follow these (see Daria Dragonscale and Kretch Tallevor) but there's another time for them.
Top tip! When renting cards, use 
League: Silver
Summoner limits: 5(Common)/4(Rare)/3(Epic)/2(Legendary)
After renting your desired summoner, just change the filter from Summoner to Monsters then select the Splinter you're interested in.
Best of luck my friend!