70% to 80% overlap, both along flightlines and between flightlines
You must have overlapping flightlines - a single flightline along a corridor will not work
Altitude depends on the resolution you want, but my advice is to test a higher flight - perhaps max altitude of 400' - because this will reduce # of images, # of flightlines, total data volume, and processing time - then run a test project and determine if you really need higher resolution --> lower altitude (which means more images, more flight time, more disk space, and longer processing time) to complete your project.
I don't know what you might be seeking in terms of image quality...? Get the best quality possible (e.g. good exposure - minimize ANYTHING that's overexposed - and proper shutter speed vs. drone flight speed to ensure you don't get blurring).
I edited my response because I forgot to mention the importance of ground control. It's always recommended if you care about accuracy, and if you're creating 3D products that need to be at the proper height relative to ground. If neither of these are important, you can ignore ground control. If you want control but don't have surveyed control that you know is accurate, you can (in most cases, pending your specific site and ability to find permanent features) extract control from the ArcGIS Online Imagery Basemap, but note the Z value extracted from the online Terrain service may be low accuracy.
