Play map 6 and 5, Season rewards if you're in Silver 1 or above, Master and Uncollected give plenty of t4cc shard crystals, become uncollected so daily crystals will give you shards, and if you're really desperate, 100% LOL, that will give you a bunch.
Find an alliance that plays Map 5 and will take your 4/40 or 2/35 roster and not kick you after one quest because you aren't good enough to play map 5x5 and hope this continues for however long it takes to make enough cats to rank up enough champs to be consistently good at map 5
Act 4 100%, Map 5 AQ spam, Expert Tier Alliance, uncollected daily crystals, and limited time events for example the gifting event that was really simple.
Comments
Easy as bro.