The Saros Armor Matrix uses resources differently. Lucenite is frequent upgrade fuel. Halcyon is rarer and deserves high-value decision treatment.
Lucenite: use it for pathing, economy and regular permanent upgrades, but avoid draining it into low-impact nodes before you know whether survival, Drive or boss prep is the blocker.
Halcyon: protect it until Second Chance and other high-impact nodes are handled. Treat unknown-effect or unknown-cost nodes as hold warnings.
Unknown costs: known effect, unknown cost is still useful. The safe rule is to rank the upgrade by goal while refusing to invent the exact number.