just to share my experience.
buy travel card if u're travelling around in taipei city. (悠游卡)
average bus fare from taipei to kenting should range around 700~800 NTD per trip. round trip cost around 1500. if u book the whole bus the price goes up to 2100 and above.
taxi fare starts from 70 NTD.
if u're looking for cheap accomodation, try 富玉庄 in shilin 士林 . get down in jiantan 剑谭 mrt station. it is only 5 minutes walk from mrt station to night market, 15 minutes walk from hotel to night market.
try to talk to taxi drivers when u arrive. they can tell u almost everything u ned to know, like places to eat. and dun eat in night market..food quality is very low in overall.

if u're looking for cheap purse/wallets with good quality, go look for a guy in shilin night market.his stall is in the center of the market, always talking '好了啦 我不要说了啦'..thn he will demo by burning his stuff with lighter. each item cost only 200 NTD.miss it, u will find same product with price of 600NTD and above..

hope it helps.