Hi - I need advice on how to handle an upcoming professional situation that I wasn't really prepared for. This is longer than I intended (over sharing?), so thanks in advance if you make it through to the end. tl;dr version: what would you buy to wear to an interview for a job you
might not want when you're in the middle of losing weight and don't have
any business attire in your closet? Any advice you have is appreciated.

Background: I've been losing weight slowly and have lost 25 lbs since August. I expect to continue to lose an average of ~1 lb per week for another 20 - 25 lbs. My loss comes in fits and starts, so sometimes I drop 2-3 lbs a couple of weeks in a row, and then go a few weeks with no change. All of this is good, but it has wrecked havoc on my wardrobe. I am apple shaped, and have lost a lot of my weight from my arms/legs, so I'm still big in the middle. I've gone from a 14/16/XL/0X to mostly a 12/14/L. For example, I wear a 12 in some generously sized clothes like Loft, but am still sized out of premium denim 32s.

I work in IT, and my current workplace just switched from business casual to plain casual (jeans allowed everyday) so I have made zero investment in replacing my business attire while buying new clothes during my weight loss. I do not own a well fitting structured blazer; I don't even own a pair of full length black trousers. I have great jeans, cords, leggings, ankle pants, jersey dresses, nice knit and woven tops, and some causual toppers (knit blazers, faux leather blazers, bomber, silky moto) that work really well for both work and dressy casual nights and weekends out. My lbd is a ponte knit sheath that is almost too big but can be belted. I am willing to add some more formal pieces to my day to day wardobe, but they need to be versatile and blend with my casual lifestyle.

Ironically, when I interviewed for my current job on short notice, I had to
buy a new suit because I had gained too much weight and none of my
jackets fit. I hated that jacket, only wore it a few times, and was frustrated that I spent the money on it even though it helped me land a great job. I've always planned on buying a great suit when my weight loss stabilizes for things like professional conferences, presentations, meetings, etc., but for now have been able to get away with the dressier end of my business casual options with a knit dress/skirt/blazer and dressy shoes.

Now for the challenge: I am happy with my job, but an opportunity has come up that I'd like to pursue. A friend works for a large company that is hiring in my area, and I'd be a good fit for many of their open roles. It could put my career back on a leadership path that I put on hold a few years ago. I'm not sure I want to leave where I am, but it's an opportunity too good not to consider. Some corporate leadership will be coming into town in a few weeks, and my friend is arranging for a meet and greet that could lead to more formal interviews.

How can I prepare my wardrobe for multiple business formal/interview situations without breaking the bank since these outfits will be short lived? I do not have a budget and can afford to spend big, but spending hundreds of dollars on something that will only be worn a couple of times hurts my soul. What would you stock up on in advance vs. buying a few days before to make sure it fits? Hit me with your expertise and best strategies, please.