what base do I order if i want a thin skin base with sfs in the front . I am new to this and dont have a clue. I want something that will be completely undectabel as well as good for working out in at the gym. I am a 23 year old male

and also what is ventilation ?

If you want a skin base with a SFS front then check off the skin base you want in the dropdown menu and specify in the 'Comments Box' which type of lace and how many inches of lace you want added to the front. Ventilation is the direction that the hair is knotted in. For example, if you want your hair parted on the left side then the ventilation would be with the part on the left and most of the hair going towards the rigth side of the unit (some hair at the very left would go toward the left side). If you order freestyle ventilation then the hair takes no set direction and can be styled in a variety of directions--great for experimenting with different styles.
Regards,
John

how many inches of lace would you recommened ? what would you recommend in general for me ?

If you're a newbie I would recommend going with an all French lace base. It' strong and undetectable. It's an excellent unit to start with and an excellent unit for experienced wearers. I wouldn't go with a combo of skin and lace right off the bat---get the hang of wearing first. You'll get a feel for lace and that's a good place to start.
Regards,
John