Can you go to $500 in terms of budget? Something like a Giant Escape, a Trek FX or a Specialized Sirrus should have a $500 price point version, and they're going to be immeasurably better than anything you'll get from Walmart at the $150-$200 price point. If you take to riding seriously, you're going to need to spend the $300 difference between the Walmart and the bike store brand bike on repairs and new parts if you go forward with a Walmart type bike. The Walmart type bikes are designed to be ridden for a total distance of a few hundred miles over their lifespan, they just don't stand up to serious riding.

When I was starting out I had a shockingly heavy Walmart type copy of a Cannondale Super V and I started riding it 10-30 kms every morning for exercise. Within a week or two it was suffering, and the death knell came one morning when I was climbing a hill and over torqued the hub; I looked back and saw a bunch of ball bearings, some of them so dry they were rolling and bouncing on the concrete path. I bought a $500 bike that afternoon that lasted me for 10 years and which is still being ridden by the guy I sold it to 15 years later. The point of that story is that a $500 bike often has components that are easily replaceable and can last for years; Walmart type bikes often have strange proprietary parts that are all but unavailable for replacement, as they just want you to buy another $200 bike instead of fixing the one you already have.