You put stain directly on raw wood, and that's exactly what you get when you do that. What you will need to do to correct is to resand the seats to bare wood again and get below the stain you now have on there. Then get fresh shellac which comes in flakes and mix it with denatured alcohol, a 2LB cut is a good place to start, and probably golden flakes instead of orange for your job. Let it sit 24 hours. The cut chart is here:

. https://www.shellac.net/PoundCutChart.html?srsltid=AfmBOoo_N_69cYBinhYU2gSW213QCqIYKVMV2JM9d8cmlCNW3rIa0NEm

Then you are going to seal your wood with shellac before adding any stain. This will slow the stain absorption and prevent those high/low dark areas that soaked into the wood. I'd try two LIGHT coats of shellac, sanding lightly after coat 1. That should give a decent seal but still allow for some stain coat. Use an oil-based stain. Gel coat can be used but it would not be my first choice. The stain will sit atop the shellac like a glaze and you can play with it some. Once you get the color coat you like, you can apply a topcoat of shellac, but then will need to finish up wiht a clear poly at shellac has no water resistance.

Getting a nice furniture finish is never a one-stop process, it's pretty typical to have to lay up layers of various product to achieve a rich and professional finish.