As for useful equipment that would really help your films right now I feel like your best use of money would be a better microphone, my mic setup is pretty weird and overkill for most folks, a lot of people like the Blue Snowball as it give much better quality then a normal headset mic for the reasonable price of $60 (keep in mind it's easy to spend upwards of $300 on mics that you will still need additional specialized hardware just to use) The Snowball just needs an open USB jack.
After sound quality what it takes to make a good film is practice. I could set you down with the gear I've amassed for the last 15 years and it wouldn't really do much to improve you're films if you didn't know how to use the gear. Right now it looks like you could focus on getting flicker free lighting and if you want to acquire more gear a few more lamps and more LEGO bricks is always useful.
Once you feel like you can get even lighting that does not flicker I suggest investing in some black wrap, gaffer tape and some light gels
For perspective a recording setup like this costs more then every piece of equipment I told you to buy combind: