I had issues with the nifty fifty in the park, it was way too zoomed for big views and not as good as expected for wildlife. Unfortunately, many budget glass options feel dark, but for Yellowstone sun youll be fine.

• Canon EF-S 55-250mm f/4-5.6 IS STM
• Canon EF-S 10-18mm f/4.5-5.6 IS STM Buy used to stay under budget and dont worry, youll do great! Let me know if you need more help.

Adding my two cents here because Yellowstone can be a real challenge if you bring the wrong gear. If you are worried about the nifty fifty being too tight, you are 100% right. On a 90D, that 50mm behaves like an 80mm lens which is basically a portrait lens... you will be backing up into a bison trying to fit a mountain in the frame. Not a good idea. Since you are on a strict $300 budget, I would suggest looking at the used market to stretch your dollar. Here is how I would play it:

• Pick up a used Canon EF-S 10-18mm f/4.5-5.6 IS STM. Dont let people scare you about it being dark. For landscapes, you are usually shooting at f/8 or f/11 anyway to keep everything sharp. Just make sure to use a tripod if you are shooting the pools at dawn.
• You absolutely need reach for wildlife, so look for a Canon EF-S 55-250mm f/4-5.6 IS STM. Its the best bang-for-buck zoom Canon ever made for crop sensors. You can usually find these for under $150 used.
• If you really want a small prime for walking around, skip the 50mm and grab the Canon EF-S 24mm f/2.8 STM pancake lens. Its way more natural for wide views. Be careful when buying used tho. Always check the glass for scratches or internal dust and make sure the AF motor isnt making weird grinding noises. Yellowstone is dusty and harsh, so you want gear that actually works before you get out there into the wild...

Ive been shooting with Canon bodies for a long time and Yellowstone is a specific beast. Honestly, $300 is a tight budget but you can definitely find some solid glass if youre willing to go used. Quick question tho—are you more interested in the sweeping valley views or are you trying to snag some shots of the grizzly bears from the safety of your car? The focal length you need depends entirely on that. In my experience over the years, you should look into:

• A standard wide-angle zoom from Canon
• A third-party zoom from Sigma or Tamron
• Any fast prime lens for low light Just stay away from full-frame glass for now because it gets way too heavy and expensive for that sensor. Those slower apertures youre worried about wont matter much in the bright Montana sun, trust me. You basically just need decent glass from a reputable brand and youll be fine.