Unless you are a local Fijian you will find it very difficult, if not impossible to get a job as an expat with Sun Air these days (formally know as Sunflower).
However, they have in the past hired expats - only as Twin Otter Captains. Fiji has ample supply of local pilots to fill Twin Otter F/O positions, likewise BN2 Captains. Air Fiji is much the same. The only reason that this might change is if Air Pacific takes another basket of pilots from the domestic scene to satisfy its continuing expansion.
At present, the only expats working for the company are the flying instructors at their flying school operation (aussie's/kiwi's).
Back to the airline side of things, pilots typically fly between 900 - 1000hrs/year. Their min requirement for BN2 command is 1000hrs total - so the progression is to start F/O on the Otter until 1000hrs is attained, then PIC on the BN2 (most of the locals that start out as F/O are from their flying school operation). Twin Otter PIC requirements are 2000hrs total, with 750 multi PIC (not 100% sure on that one).
The flying is fantastic in terms of scenery and challenging conditions. Lifestyle is pretty relaxed which can become somewhat frustrating at times when you are trying to do a professional job. Maintenance of aircraft may come as a slight shock if Cumming from Aust/NZ.
Summary - Flying in another's country in my opinion will always be good experience to progress your career. The flying is good and as long as you are careful, you'll take away a wealth of experience and knowledge. If you can last a considerable amount of time in Fiji, this may go a long way in securing a position with a major airline that employs other than locals - eg Cathay.
Good luck