hi all . I am still new to online stock trading process. Need help from all the pros here

I am using CIMB ITRADER.

i buy in at my desire price say ' 1.50 '. whats the limit i should set in ? and should I choose todays date if I want to proceed the 'buy' immediately ?

and lastly, say the current p[rice is '1.50', why there is a different in buying and selling at the left box ? the lower price you choose to buy in, the higher the selling price? whats it means?


thanks in advance