What are simplified characters and traditional characters? Which should I learn first? In which sequence should I learn Chinese. What are simplified characters and important traditional characters which should I learn first and why those are necessary to learn first?
only if, you're interested in history, culture; or, you need to read materials dated before 1949; learn traditional chinese.

otherwise, learn simplified chinese first. particularly for anyone who learn "chinese" for bread-and-butter.

it's "easier" to read &amp; write; for foreigners; compare to traditional chinese.

to be fair, well, there's a chinese proverb "物以罕為貴"; it's roughly "when a thing is scarce, it is precious".

have fun :)