its a difficult balance, you want to entice your audience early on, showing that you're not just a great writer - but depending on game mechanics, if you need to grind 'points' one way or the other, or if its a VN with a set story arch.
I don't play beyond 0.1 if there's no sex scene, with the multitude of other options, why would I want to get blueballed?
That sex scene need not be the full combo of sexual interaction with a main LI, but could be something that becomes a driver for further history - for instance: MC has a vested love interest in a girl, but her friend has the hots for you and at some point her friend manage to get MC drunk/drugged/horny enough to do something sexual with MC - how hardcore that thing is should depend on the setting you're going for. If you're making a fuckfest, you're making a fuckfest, but if you're angling for a more 'realistic' approach to relationships and sex, then having MC and LI's friend making out, maybe a handy or similar, could be a good start and a good setting for some intrigue.
Meh, as said its difficult, so many variables that need to be taken into account, but showing sideboob and bikinibottom just ain't going to cut it in this market

Thats just my two cents, best of luck going forward.