Hi there ,
I'm no gmat expert but for a 600 i am sure i can be of help
For Quant - get hold of the Manhattan Pdf's , solve them to get a grip on your basics , if you feel like you don't want to spend , i would suggest you to download GMAT CLUB math book , that would cover all basic quant formulas and solve
GMAT CLUB tests , if you feel you like you don't need to spend money then use the forum's question bank / ps /ds section , loads of questions to try
For Verbal - though i'm not a huge fan of
E-gmat if you can afford the course , please go ahead and purchase , else get hold of Manhattan Pdf's . Read them n write down the rules and tips you come across
get yourself an
OG guide , solve them along with the pdf's available on gmat club
look at the download section in gmat club , a lot of 700-800 level SC /CR /RC questions to practice . If you can do purchase Aristotle or get hold of Veritas PDf's . A good bundle to solve questions
Once you are done with Manhattan SC/CR/RC and quant prep , take a mock download gmat prep and asses yourself . If you can purchase do buy Manhattan mocks , they are one the best mocks in the market
After you are done with your first mock , analyse your mistakes n book a convenient slot and work towards your target score
hope this helps
KUDOS if you think it helps
Regards,
HK