I have gel false tips put on over my own (very short and weak) nails. They stick the tips on, file them smooth to my natural nail then paint them with the gel lotion. That dries quickly, then I have them painted with normal polish - either OPI or Orly - two layers followed by clear topcoat, then they go under the hot air hand driers.....They grow out a little from the natural nail after a few weeks (they say fortnightly, mine last a good three or four weeks) so I have 'infills' which means they fill in the little gap with more gel lotion and file them smooth again and polish them again. I only need new tips about 3 or 4 times a years......New nails cost about £30, infills are either £15 or £17 if one is split and needs replacing......
They are very durable, occasionally I chip or split one but not often and the polish
usually lasts from one visit to the next although you can easily buy nail polish remover from any chemist and paint them yourself, I have done sometimes
I think shellac is painted on over natural nails but no false tips are involved, so a certain amount of natural length is required..................