To create different individual drive time buffers you can't use BUILDER, as it's not parametrized by a field. Instead, you need to use SQL directly to
UPDATE your dataset with the geometries. So if your field for the commute time is
commute_time then your query would look like the following queries. Mind that I'm putting the points as latitude/longitude to avoid having to use two tables.
I will do the process from scratch creating a table and adding some fake data, you should only have to apply the last query adapted to your scenario.
Create a testing table:
create table testing_driving_time (
Add some testing data:
insert into testing_driving_time (commute_time, latitude, longitude)
And finally compute the driving times using the Data Services API
set the_geom = (