I have the correct size gaiters and I started off wearing them under my waterproofs and when I stopped wearing waterproofs I then wore them over my walking trousers but under my rain skirt. I then discovered I could stay dryer for longer by wearing my gaiters under my walking trousers. For me thats been my most effective move.
My leather shoes now do leak, along the sole to boot join, but I have new waterproof boots which haven't leaked at all yet, which is why I now know for sure that my Rab gaiters leak. Prior to my 11th November 2018 walk I used my new boots in the rain and found only my calves were wet, my feet were dry. As it was that time of the year I used my old but 'trusty' leather boots for Great Gable, that was the first time in over two years that they had leaked and I must admit, at the time I was most surprised.
I also do 'proof' my clothes, especially my Paramo, usually about 2-3 times a year. Its a good jacket, no doubt about it, but for me, too heavy, too hot in the warmer months and for good rucksack packing, too bulky. I moved on to the Marmot Precip, much prefer it.