Brake Flaring Tool....Best to Buy???

If doing brake lines you must double flare.
Mine is MAC but l have had it for probably 30 years.
I see them at swap meets and flea markets all the time. Just be sure the double flair inserts are included.
Keep in mind that " standard" brake lines are 45 degrees and AN fittings are 37 degrees in case you are using them as well.