Fusion research is actually very well funded. It doesn't seem that way because nearly all news stories about fusion are about the Q factor of the latest shot or experiment was. (Q is the energy gain factor.) The field is advancing on many fronts, using several strategies. ITER is but one of many efforts. Some results coming from NIF suggest that ICF is not as dead as it seemed years ago!

ITER itself is (iirc) the largest scientific project on Earth. It is funded by 35 countries, to the tune of billions. They have already had cost overruns (the perpetual curse of modern science it seems) but I doubt that more money would necessarily solve fusion engineering faster. They are currently building the reactor and are on track for first plasma in 2025. An ITER-scale tokamak is as close to a "sure bet" for Q>=1 that you can get. (Their goal is Q=10)

Interestingly, one of the major milestones for ITER is tritium production through breeder blankets - which would solve a critical bottleneck for future, enterprise fusion power systems. (Not to mention scientific research.)