Best budget option: Flydubai — Why

• Flydubai is the main low‑cost carrier operating direct Colombo (CMB) → Dubai (DXB) service with frequent flights and the lowest published fares on the route compared with legacy carriers. (Flydubai.com)

Other carriers to consider

• FitsAir: a smaller carrier that sometimes offers competitive fares on CMB–DXB (less frequent service). (flightsfrom.com)
• SriLankan Airlines / Emirates: full‑service carriers with more inclusions (checked baggage, meals, more generous change/refund rules) — often pricier than Flydubai but sometimes comparable during sales. (flightsfrom.com)

Practical tips to keep costs down

• Book directly on Flydubai’s website or a meta‑search engine when you know your dates — LCC fares fluctuate and seat availability is limited. (Flydubai.com)
• Watch baggage and seat selection fees: the base fare often excludes checked luggage and advance seat assignments. Factor those add‑ons into the total price. (Flydubai.com)
• Be flexible with travel dates and fly midweek if possible — cheapest fares usually appear outside weekends and holiday peaks. (Flydubai.com)
• Compare total cost (fare + baggage + change fees) against occasional sales from SriLankan/Emirates — sometimes a full‑service fare is comparable and easier if you need baggage included. (flightsfrom.com)

If you want, I can:

• Check live fares for specific travel dates and show the cheapest options (I’ll need your departure and return dates), or
• Compare total costs (including baggage) across Flydubai, FitsAir, SriLankan and Emirates for a date you give.