Since I can’t afford the i5-8400 should I not go with the i3-8300?

The i3-8300 is pretty great. Been running it on my rig for a couple months and it runs games nicely, if thats what your going for. Also i am running a GPU which helps. I can run modern games on medium settings some on high depending on the game, with no problems.

Low resolution it will handle fine, yet wouldn't recommend for quality reasons. It might stutter and cause headaches. 7700K, 8700K would be better in that sense