Op it’s hard to advise without knowing your size and height, if you’re a sixteen and six foot or a size twenty six and five foot.
Or what your budget is
I live in a quite rural area with a lot of wealthy horse owners, and as much as absolutely no one is running around in tweed, the easiest way to replicate would be
A pair of long line wellies like hunters.
A gilet,
A long line shirt or jumper, possibly a long line vest under it.
A pair of skinny or straight jeans or leggings, Maidenhead fat free leggings from amazon are great for disguising lumps and bumps.
As much as many folks still wear boot cut, and in some fashion circles they are coming back, they are generally still seen as really quite dated.
If however the fundamental issue is you’re uncomfortable with your general appearance and are looking at other women with envy because you’re not feeling good and trying to cover up, then focus on doing something about that. It’s hard to comment without further info.
However that’s the main uniform of the horsey set.
Hunters type wellies, gillet, long line shirt or jumper, leggings, jodhpurs or skinny jeans.