I'd follow the advice below. Building a basic block explorer will demostrate that you understand most core concepts of Bitcoin, a spv wallet will back up your credentials even more by diving into the security of cryptocurrency. An exchange is probably something I would consider very last on your resume. If you want to have a good resume, its best to start from the foundations, and then continue build from there an exchange is not touching on a lot of cryptocurrency foundations that are probably good to understand if you're specializing in cryptocurrency programming.
If you're aiming at the commercial route of building exchanges, I would still advise getting some basic wallet, and block explorer out there. Technically, if you're developing an exchange you'll be needing some functionality of a wallet, and some functionality of a block explorer for the exchange to function.
You could try to build a basic blockexplorer, a DEX, casino game, a spv wallet, or just try to think out of the box and be creative.