PrincessBarbie, put breeding completely (COMPLETELY) out of your head right now. I cannot stress this strongly enough. I think you have come to understand that while willing to learn, you are very much a novice, when it comes to horses in general. You need several more years in horses, before considering breeding your mare.
Many of THE most knowledgeable horse owners on this forum, have yet to breed. Some with vast knowledge under their belt, have bred and been disappointed with the outcome, even with a ton of homework. Others, know their horse have faults which they do not wish to pass on. Some, who waited, did their homework, chose exactly the right stud for their mare, had the correct facilities and enough money saved in case of a disaster, ended up with a dead foal. Some ended up with a dead mare and foal. Breeding is not for the faint of heart and every time we breed our mares, we know that the worst can and does, happen.
I can tell by all your posts, that this little mare is dear to your heart. You want to have her for many years into the future. I think many of us here, have also come to like your little girl very much and we want the best for her and save her and indeed you, from problems.
So lets do it this way. Plan only for the next year and starting now. Work on getting her into a favourable facility. Work on planning an absolutely solid feeding plan and stick to it. Start her ground work. You can do this yourself by obtaining CDs from (for example) Clinton Anderson's correct ways to start young horses. You really do not need a trainer for this. In your spare time, learn, learn and learn. Keep notes if you need to. If you are really dedicated and I believe you are, you will be surprised at how much more knowledge, you will have under your belt, a year from now. And I'll bet your filly will look tons better.
If someone tells you something you are not sure about, just ask here. You know already we will help you. Keep and take good profile shots of your filly, starting now. Take one per month and you will see the difference.
Certainly take riding lessons yourself. It will give you a great 'feeling' for horses in general. Whether learning English or Western, will be up to you.
Try both and see what appeals to you.
You may end up training your mare under saddle and never thinking of breeding. After a few years with a lot more knowledge, you may come to realise that your mare isn't even breeding quality. The majority of horse today are not, but still make wonderful riding companions.
Certainly, after a few years, evaluate your mare and ask others their opinions, as to her quality. Only then, and only if she is breeding quality, start looking for stud horse who compliments her. The stud will need to be correct where she is not, and vice versa. Even if you like certain stud horses now, if and when your mare might be ready to breed, those horses could be dead and others more suitable coming along. Things change constantly, when dealing with live animals.
You actually have some fun years ahead, even though at the moment, it might seem a bit daunting. I know I have been rambling a bit here, but just trying to give you an idea of how I'd love to see you proceed. I've shown dogs for 60 years and horses for a little less, but I'm still learning every day, even though my health now, doesn't allow me to do either. It really does become a life-long committment.