I have an HP Pavillion Gaming laptop, 15-ec0xxx

I'm fairly certain it has a slot for additional ram, and an internal HDD if I want to.
Currently it has only 8gb ram, 256gb SSD, along with the GPU Being a 1050 and the CPU being a Ryzen 5 3550H 2.10GHz

I was wondering if it's worth it spend around $250 CAD on a 2TB HDD + an additional stick of 8GB ram, or if I'm better off saving my money until I can buy a 1000-1500 dollar laptop that has better specs.

I bought this one last year during Black Friday for around $550 CAD so it was a really good deal.

I prefer desktops 100%, but my desktop at home is doing fine and I need my laptop for work (I game at work because my job is very lax).

I don't play very demanding games, but I do enjoy having more than 1 window of Runescape open at a time, alongside other things so I figured the ram might be nice - however I'm not sure how much of an improvement it would make for $100+, and whether to invest into this laptop or not. Lately i've been noticing some frame drops if I have too much stuff open at once, which is something I got used to being able to do at home.

I've never upgraded a laptop before so I'm very curious about what you guys think. Thanks in advance, sorry for the wall of text.

TL;DR I have a laptop with 8gb ram 256 SSD, is it worth buying 8GB more ram and a HDD or should I just wait until I can afford a better laptop.

upgrade the ram skip the hdd unless you need more storage

Can I add a 16gb for 24 total or is it better to just add a second 8? I remember being told to generally use all the same sticks

pretty sure it has to be same stick
16 should be fine if youre spending more then might as well upgrade to newer laptop theres been some decent deals this weekend

Thanks

You do not have to match sticks although its advised cause sometimes you encounter issues.
Additionally if you run one stick that's 3200 and another at 3000 they will both run at 3000.
Your best bet would be to buy a single matching stick provided you have 1x8gb stick atm and not 2x4gb sticks.
Otherwise go with a set of 16(2x8)/32(16x2)gb kit and sell old stick.

16GB of RAM should be more than enough for a gaming laptop.

Don't see the point adding in a HDD. More heavy, more noise, consumes more power (important if u use battery and not charger) if u have extra cash replace the SSD with a 1TB SSD and put the stock SSD in your old xbox/playstation (if its a SATA SSD)