Blueberries are the year-one engine
80g seeds, 13 days to maturity, then regrowth every 4 days with a yield of three berries per harvest at 50g each. Over a full summer a single bush produces around 22 berries — about 1,100g from one 80g seed. Plant them the first day of summer; every day of delay is pure loss.
Melons pay for the bundles
Melons (80g seed, 12 days, 250g) are slower and single-harvest but three of them are required for the Quality Crops bundle, and melons have a chance to become giant crops for bonus yield. A mixed field of mostly blueberries with a melon block covers both money and progression.
Starfruit for Oasis players
Once the bus to Calico Desert is repaired, starfruit (400g seed, 13 days, 750g sell) is the strongest pure-gold summer crop. Hops on trellises are the sleeper pick — daily 25g harvests from day 11 onward add up enormously, but the trellis blocks walking so plan the layout before planting.