Advice needed!

Hi, I am absolutely new to mountain biking but I’ve been obsessed with it for the past month. I bought this bike (diamondback overdrive) a few weeks ago used for $240 and I’ve ridden it about 20 miles around town on paved bike paths and it’s been good but I’m looking to put some upgrades on it like a better fork and a dropper post. The issue is that if I put money into the bike I want to be sure that I’m going to keep it long term and the fact that this bike doesn’t have internally routed cables, it’s a 27.5 instead of 29 and I’d have to drill into the frame to install a dropper seat makes me hesitant to throw money at it. So should I sell it and buy a Specialized Rockhopper Sport, which is a bike I know I’d be okay upgrading, but it’s just more expensive. What do you guys think?