Agreed, you do not want to do sound design or mixing or mastering on laptop speakers... i did read the OP as he was mixing on a separate system. IF the OP is mixing on laptop speakers, yea you need to get some monitors, a sub, and some room treatment, could be basic like 4 reflection panels and two bass traps, to start. When I decided to make this a serious hobby, I invested in 250 sq ft of rockwool (250$ worth?) and did my own floor to ceiling corner traps, four side reflection panels, two front panels, four rear panels, two bass traps, and 4 cloud panels. I also built a wall in my room, to make the room not square, to give it a ratio that was acceptable for sound application.
You dont want a room that has dimensions that are the same, even, or multiples of one another. my room is too small, like most home studios, but it is to scale of the golden ratios. I have an 11 ft wide x 13.5 ft deep x 8.5 ft tall room. the wall I made to close the width down to make it rectangular. its a cheap wall, made out of 1/2 x 1 inch strips and sound absorbing board. The size and shape of your room is one of the most crucial parts of a studio when it comes to the goal of having a decent bass response when mixing with monitors. basically any room you put speakers in, that room becomes a speaker cabinet, and with different size and shape come different sounds. reflections are always going to exist, so its managing these to create a sweet spot, where you are neither in a null or a void.
I went with larger monitors because Im aware and intend to do my stuff at a lower volume... i have owned 5 inch and 8 inch monitors. i will say the 8s are nicer, but they are louder. and the 8s have better bass but no where good enough to mix from. you need a sub, at least depending on music... i do. 40-80-120 hz is the low end where most speakers loose their accuracy and drive. a sub is designed for these applications. mine is hardly on... lol its so powerful and loud in my small room. which is perfect! i like to mix at lower volume, around 60-80 db depending, usually im around 70 db or less for constant mixing or sound design. right now, im sorting the maths to get my room analyzed. i know i have a 44 hz standing wave... this was amplified by my triple computer screens, and once i removed them, using one, the sound can go thru the area between the screen adn monitors, which took away the front live area, with a bad bass boost. this recent change i made has drastically improved my sweet zone and my mixing!!! I did move the monitors from 6 ft wide to 4 ft wide and wow, the difference was 100% better! just one idea to help with finding that sweet spot!
There is a lot to learn and a lot that can affect how it sounds where you sit, where the monitors are positioned off the side walls, front wall, etc.