Matt J.
for me, cat cow, forward fold variations (sitting, standing, one leg, wide-leg, etc), lunge stretches, supine twists, figure-four stretches, and child's pose are my top-tier stretches. they're the best for both improving flexibility and easing muscle soreness/tightness without being difficult or uncomfortable. i write my own stretch series, and at least one of those stretches is in every single one. my split-training series uses all of them