You can easily make your lashes longer & darker by using normal mascara, without looking like you're wearing mascara. I'd suggest getting one that doesn't flake at all, firstly. Because that'd be an immediate giveaway. Most non-waterproof mascaras I've tried, even more expensive ones, flake. So I'd suggest getting a waterproof product. L'Oreal Double Extend waterproof formula is great stuff. One end is a base that lengthens & thickens. The other side is the mascara. It would also help to get some mascara wands. You can get a bag of them very cheaply online. Or you could go to a MAC store & pick a couple up there for no charge. Just be sure to buy something while you're there to avoid coming off as rude. You also don't want them thinking you just came there to steal their wands
They always have mascara wands for applying their products in-store. I always ask for some when I'm there shopping. It's never been a problem. You'll need several, but the great thing is they can be washed with just soap & water & reused many times. It's also good to have a mixture of different shapes & sizes for top & bottom lashes, as well as to get them looking as natural as possible. Wash them after each use as once the mascara dries on them, they'll be hard & crusty & very difficult to use again. You can leave them soaking in soapy water while you're out so they're easy to clean when you get home. I've also found that vegetable oil removes the mascara fast for quick cleaning. Then just rinse them with soapy water & let dry. Rather than using the brush that's built into the mascara itself to apply it, use your wands. Dip a clean wand into the base side first, get a little bit of product on it - wipe off any excess - and apply. Immediately after applying, comb your lashes out with another dry, unused wand, trying to fan them out. That'll leave just enough product on your lashes to thicken & lengthen them without looking caked on. Next, take another dry, unused wand & dip it in the mascara itself. Apply it to your lashes over top of the base. Once again, immediately comb your lashes out with a dry, unused wand, fanning them out, until you're left with more enhanced, natural looking lashes. I do this when I'm wearing very little or no makeup & it always turns out great. You can easily use black mascara & still have your lashes look natural. But I'd avoid using brown. Most peoples lashes are either black or brownish black. So if you want to avoid black mascara, go for a brownish-black shade.