Most profitable items are
Trending items (2017 fidget spinner/ cube was popular, i used to pay 50 cents from china and used to sell it for $15 to $20 in the beginning. Most i paid $5 on each and made $50 on each)
Ladies makeup items (they are cheap, nail polish, nail stamper, make up kit usually cost less than a dollar and can easily make $10 to $15)
Phone accessories (iPhone accessories, ring, pop sockets, stickers, case usually cost 1 or 2 dollars and can sell it for $10 or more)
Stuffed animals (popular character stuffed animal have more 2000% profit margin)
Seasonal items [holidays (items for Christmas, Easter, fourth of july, Halloween), fashion, recreation (ski gears, snow gears), back to school (school’s supplies)]

Clearance items (anything you can find on clearance, first check piece in amazon and eBay)
Disney items large and small are very popular on eBay and amazon ( usually I buy from clearance or closeout)
Shoes (go for the clearance)
Package food and spices (Ethnic Food Like Nepalese / Indian / Middle Eastern/ Africa)
Cloths are profitable (if you buy in a big lots)

Bulk considered if you buy 1000+ pieces which usually cost thousands of dollars and storage place. Start with small if you're starting new online business.
If you still want buy bulk alibaba.com is popular