This topic, or a variation of it, seems to come up on here pretty often. The bottom line is that none of the OTC products are going to come anywhere remotely close to what you can get done at the dentist. While the strips may seem really cheap compared to having trays made, you will see minimal results and you'll end up spending more on strips over the course of time. Not to mention, a lot of the OTC products are terrible for your teeth and will leave them super sensitive.
Save up $300, go to your dentist and have trays made. That price will include a 4-pack of 15% solution. And you can go back anytime just to purchase solution for like $25/4 pack. I recommend getting the 20% though, which is the strongest they'll let you take home. I used 8 total tubes over the course of a few weeks and my teeth are bright white despite being a heavy coffee and red wine drinker. I had to stop using it actually because a couple people told me they are starting to look fake from being so white. Once you get to the shade you like with the trays, you only have to do it like once a month, if that, to maintain. And I have no sensitivity issues at all. They'll tell you to only use the 20% for 2-4 hours but I slept with the 20% in and had no problems.
Strips are okay if you are on a budget and want to maybe improve one shade, if that. Trays will take you 5+ shades whiter and the results last a lot longer. They'll pay for themselves with what you're gonna blow on strips over time. Best $300 I've spent on any cosmetic product/service.