jenna, if you're truly serious (compulsive?) about crosswords you probably
do need to purchase Chambers. [Especially for barred puzzles like Azed, for which it's essential.]
I stubbornly do without, as I want crosswords to be a sporting hobby, but every so often I either have to go on faith (as with 7 today) or miss a solution altogether. I can generally tell when it's a matter of an obscure Chambers issue word, but the solution often escapes.
And I pass on Azed and the Chambers-intensive barred puzzles.