What I do....loosen the cast control knob, the one that puts tension on the spool, located on the crank side. Loosen it to where the spool will move side to side. Then tighten it to just where the spool stops moving side to side. This is as loose as the spool tension ever needs to be. Go tighter if this is too loose and backlashes are just constantly happening, but never go looser.
Then I set brakes to help with backlashing. I use more if it's windy outside, and less if distance is greatly reduced when casting, but most of the time I use two brakes, or three on heavier baits where backlashing happens more often from harder casting.
The thing you've been told about using brakes in even numbers is bunk. You can use any number needed, even odd configurations. None, just one only, or two, three, five, and so on. Some people do recommend even settings for balance, but even three fits into that also, in a Y configuration. That's three on, three off, on reels that have six brakes. With 7, that's not possible, but 7 is an odd number anyway so it must be possible to use odd setups or they couldn't make the reel that way. I also saw that this reel has two sets of brakes? Not familiar with that. Mine all have just one set, or are magnetic only. I'd turn one set off completely and use maybe 3 on the other set, with the spool tension set like I described, and either add to that or take away as needed. Start with small casts and add distance as you gain confidence. Start with streamlined baits that don't catch air as bad to get a feel for casting. They cast easier. Things like jerkbaits, crankbaits, or a jig even. A spinnerbait with blades and a skirt will catch air and cause backlashes if you're not experienced at casting them. Go to those after you learn to cast easier baits. If you get massive backlashes with the settings like this, even with lots of brakes on, then tighten the spool tension knob some. Remember, a little here goes a long way. When I ever tighten mine, I just barely move it, and then barely move it again if not enough the first time. 1/4 turn of this knob is WAY too much. I'm talking 1/16, if that.