Do I really need a separate weighted base?

For market umbrellas, yes—reviewers on r/homeowners specifically recommend roughly 80 lb bases for 9 ft umbrellas and 200 lb for 9–10 ft offsets. Several cantilevers in this roundup include a fillable or sandbag base, but Reddit and verified-purchase reviews consistently warn that under-weighted bases are the single biggest cause of umbrella failure in moderate wind.