Getting to Tuvalu takes real effort, which is part of why so few people do it.
By air is the only realistic option for most travellers. Funafuti International Airport (FUN) is served by Fiji Airways, which operates three flights a week from Nadi, Fiji (Tuesday, Thursday, and Saturday), taking about two and a half hours. Tickets are expensive relative to the distance — expect to pay USD 300–500 each way, and book well in advance as seats are limited and the schedule does not change much. Air Kiribati flies weekly from South Tarawa, Kiribati, which gives you a second routing if you are already in that part of the Pacific.
The most practical approach from Europe, North America, or Australia is to fly into Nadi, Fiji first, then connect onward to Funafuti. From Sydney, expect a total journey of around eight to ten hours including the connection.
By sea is theoretically possible if you have access to a yacht or can arrange passage on a cargo vessel, but there is no regular passenger ship service connecting Tuvalu to the outside world. The government vessel Nivaga III (which replaced the older Nivaga II) occasionally makes runs to Suva, Fiji, but it is not designed for or marketed to tourists.
Visas: Most nationalities receive a free 30-day visitor visa on arrival. You will need a valid passport (at least six months beyond your planned departure), proof of onward travel, and evidence of sufficient funds. Longer stays require an extension application at the immigration office in Funafuti.