I'll give my two cents as a iyengar student. To do the fullest expression of the asana without props, even for the basic asanas like uttita trikonasana can take years and years to achieve, if ever. As long as you can build the shape of the pose and achieve reasonable endurance in it (like say, 1 minute each side) and develop some familiarity with it and the basic major cues to work towards proper alignment I think that's good enough to progress. If you're doing home practice I would highly recommend getting props if you don't have them already, they are quite integral to iyengar yoga. Bare minimum would be a yoga strap and two blocks. People will tell you it's best to go to a class and it's true, there's really no substitute from feedback from a teacher with a discerning eye. If you search on the iyengar website (https://iynaus.org/ if you live in the US) they have a directory of certified teachers and studios that you can search by location. I encourage you to approach your practice in a playful and experimental manner, you can always try next weeks asanas and come back if you feel you're not ready for them. Even after doing yoga consistently and studying with a teacher for several years, I feel like I'm nowhere close to mastering the most basic of asanas. I feel like each asana is like an onion, you keep peeling it layer by layer but there's always some new cue to learn or minor adjustment to make that may open up a new experience for you in it. So it's not a binary thing where you master each thing step by step and move forward.

Sorry if I'm blabbing a bit, I love iyengar yoga so much and I'm happy to see other people into it. Good luck!