A gram should be a lot more than 10 lines unless it's just total garbage. That said, I have a few times before picked up garbage street grams where a gram would indeed be 10 shitty lines... so if you're sure of the absolute rock bottom quality of your cocaine - or perhaps if you have a super high tolerance (although if you did, presumably you wouldn't be asking this question) - then we'll go with that. Otherwise if you're just pulling this number out of the air you should be hoping to get around 40 lines of 25mg each, maybe more, maybe a bit less, but roundabout that region.
Anyway, I would suggest doing them as infrequently as possible, probably you'll want to dose more frequently than every 2 hours, but just do one... wait a little while... and see if you want another. In my experience cocaine has a fairly narrow range of good feelings, you don't want to dose too high because when you start coming down you'll probably feel quite bad and want to dose just as high again to counteract the bad feelings, and thus probably ruin your session somewhat. You also don't want to dose too low because, well, it's just pointless, but definitely preferable to dosing too high because, as the saying goes, you can always take more, but you can't take less. So start cautiously and feel it out. Again, start cautiously. I think that's the most important thing both for your own safety and so as to actually have a fun time rather than an exhausting few hours of up-down fiending followed by a grinding crash.
