how to ensure at least 450 in gmat

i need to score 450 as this is the official requirement for my ms-is program.

can anyone please tell me whether these books will be enough? i'm yet to buy them.

1 ) everything verbal ( rc / sc / cr / essays ) and strategies / shortcuts - princeton

2 ) maths / ds / graphs - barron

3 ) practice tests - gmac official guide

i've heard that kaplan is not worthwhile for studying purpose as there are no tricks discussed and all the maths problems are done using step-by-step approach. also, the difficulty of practice tests is a little less than the gmac official guide, so is it still wise to buy the kaplan just for the sake of practice?

do i need to buy all the three official guides ie official guide for gmat review, official guide for gmat verbal review, and official guide for gmat quantitative review - or the first one compensates for second and third?

and which set should i read just before gmat - ONLY the official guides OR ( princeton + barron )

for toefl ibt the official requirement is 79. i'm studying from these books - are they enough to fetch me this score?

1 ) barron 2 ) kaplan 3 ) ets official guide

and which book should i read just before the toefl - barron, kaplan, or ets?

thanks in advance.