The best breeches, helmet and boots are the ones that fit you best. If you give some sense of your proportions people can send you recommendations. I mean I have short full calves, I have a larger oval head, I am a solid 32 in breeches, so my brands are determined by that. The only thing I’d say is the new MIPS technology in helmets seems promising. Also I have ended up wearing paddock boots and half chaps way more than tall boots.
Other than that, the best saddle for you is the one that fits you and your horse. Seat size is driven in part by femur length. Do you like and open or a deep seat? Big or small blocks?
My advice would be to always shop for a high quality second hand saddle over trying to deal with the pressure sales and fitting hassles of ordering new semi custom. Any of the quality semi custom saddles will be an excellent choice if they fit you and the horse. Every brand tends to have it’s own tree shape. It’s not just wither gullet, it’s the front to back curve. Find the brand that matches your horses back. Passier, Schleese, County, Stubben, Black County, Custom, etc would all be fine if they fit. Or did I just say all this to you on another thread?
I am a huge fan of buying second hand and not overbuying. You will want to wait on your saddle pads until you know if you will require any shimming with your saddle. Likewise buy the turnout blankets or rain sheets that you actually need based on climate and horse. Make sure to measure your horses head before buying bridles.
You might already have figured this out, but in dressage people really do save their white breeches and pad for showing, and school usually in darker neutrals. I feel like jumpers are more likely to school in beige breeches, or lesson kids with one pair of breeches will make them basic beige.