Microsoft Rewards and survey sites are the two most legit free-Robux paths. They work very differently: one is passive and slow, the other active and fast. Here is the math so you can pick — or stack both.
Microsoft Rewards: the numbers
Daily searches and quizzes earn roughly 150–250 points a day. A $5 Roblox gift card (400 Robux) costs about 5,000 points — so figure 3–5 weeks per card at casual pace. Zero effort beyond searches you already do, but the ceiling is low.
Survey sites: the numbers
FreeRBX pays ~120 points per quick survey and up to 1,500 per offer, at 10 points per Robux. An hour of focused surveys can clear 400+ Robux worth of points — what Microsoft Rewards takes a month to deliver.
The verdict
Do surveys for speed, keep Microsoft Rewards running in the background for free. They stack: run daily searches passively, spend one focused evening a week on surveys, and you cover both channels with minimal total time.