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You're off to a great start with natural lighting. I don't think spending €150-200 on a large aperture lens will do much when there is no background to blur out.
I've not done much product photography but know that lighting can also be expensive. You could try using reflectors to create some fill light and lift the shadows. You can experiment with this on a small budget, e.g. this is £9.99 + postage. https://www.wexphotovideo.com/wexpro-30cm-collapsible-reversible-reflector-silverwhite-1584765/
If the natural light isn't strong enough to really reflect.. you can think about adding light, try a DIY softbox. https://www.diyphotography.net/how-to-make-a-diy-softbox-for-almost-0/
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These are all solid. If these are just natural daylight then think about what's around the subject. Daylight changes colour depending on all sorts of things like time of day / weather etc. Nearby surfaces also introduce colour. If you want to have consistent colour at the time of exposure then a light source and some kind of controllable space. You could build a very simple frame with some wood, an A2 sheet of white card for the background, white tracing paper for the sides/roof. You could stick some kind of stand out from the background to mount products on so they appear suspended and so you don't have to worry your body introducing colour/shadow/fill etc.
If you're considering a buying a light/lights then remember that cheaper (and even more expensive ones) will introduce some kind of colour that isn't actually white so if you're trying to minimise the amount of post production then adjust your settings in camera accordingly.
Personally I'd stick with things as they are.
Are you using any external lighting? I'd start there - would also be good to see some examples of what you want to achieve.