The blockchain doesn't compress very well so I'd advise against trying to compress the directory. The easiest thing to do is prune your blockchain which gives you a fixed size blockchain of only the latest blocks that fit into the size you specify. The smallest you can set it to is 550MB. You won't be contributing to the network as much since you will no longer be able to seed new nodes, but it depends on what you want to run your own node for. If it's only for your own security and wallet then you won't lose anything by pruning it. Set prune= in your bitcoin.conf to the size you want.