Collecting 3/4/5 stars as Valiant

So I am a collector. I value a full collection more than 7* r4s and r5s. Before today, i would trade in all my incursion currency for a load of 3/4 star crystals, and every week, and id also max out the 5 star crystal shards in the BG store every week

The new essentia store doesn't have any 3/4/5 star crystals/shards for purchase. So how would a Valiant player obtain these lower rarity shards?