I try to start new folks out on skeet with all singles on the skeet range. You don't have to worry about pumping the gun on doubles. Once they get comfortable with the targets and if they are consistently breaking the majority, then I will move them to doubles. Watch several rounds of skeet before you just jump in not knowing what is going on, maybe find a member of the club that looks like they know what they are doing and ask advice, most will be happy to help a new shooter even with a self defense/riot gun. Many times they will offer to let new shooters use one of their own guns. I have 2 or 3 guns set up for kids with a shorter stock just for this reason.
If you do decide to use your home defender find some shells that are called ultra-lights, generally will have 1oz of shot with a velocity of 1200-1250fps. Nice mild target shell, I use mostly reloads that I run 7/8oz of shot at 1200fps, the equivalent of a 20 gauge shotshell, not only is there no kick, I save money on reloading less shot. I am a 6' 2" guy at 280lbs, I don't need low recoil, but I prefer it to get on target for second shot quicker.
Fatigue will get to new shooters quickly, holding a shotgun out in front of you for extended periods of time is tiring, recoil is also fatiguing, eventually gets to the shooter. Find a coach or another shooter willing to help and not go too fast to show you leads and footwork on each station. I often teach new shooter the basics and sometimes will find a new shooting buddy this way, I am not a "coach", but have shot well over a half million skeet targets and am pretty good at getting people to hit targets on a consistent basis.
If you really think you need a new gun to start with skeet, you should really find a club or gun store that caters to clay target shooters and has those type of guns in stock, any times there may be a good used shotgun that someone traded in to upgrade, or a kid outgrew. I tend to think long term with a target gun, like the shooter will be hooked and shoot several thousand rounds a year, but many will try a few rounds and maybe shoot 100-200 clays a year and a cheaper shotgun is fine for that, but quality will generally last for the long term shooter.