I was taught to pick locks and padlocks 10 years ago by a chap who was ex-British military intelligence. I had three guys from the Serious Fraud Office sitting behind me at the time. I was on an Certified Ethical Hacking course and the trainer liked to keep us busy with some extra curriculum activities during our lunch break :)
Up your budget a few quid and get one of these .. ABUS Outdoor Key Padlock TITALIUM 64TI / 40 https://www.amazon.co.uk/dp/B007VL74I2/ref=cm_sw_r_cp_apa_oUbPBbTXW58DC
You get what you pay for
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You don't need a grinder, my mate managed to open this way a £20 - so pretty decent squire padlock