I am working at my desk for 10h+ per day. After I started my freelance work in my own office and a longer period of sickness due to back problems, I searched for the same topic. In the end, I got an electric standing-sitting-desk base for around 500 bucks and put a 2,5m tabletop on myself - the prebuilt and "professional" electronic tables were 1k+ for the cheapest and that was too much money back then.
I switch positions a few times a day between sitting, standing and standing/sitting on a bar stool (according to the research I read before buying, it's not the sitting that hurts you most - it's staying in the same position for too long). Also, I now put 3 small water bottles with magnesium on the table and try to drink them over my workday - helps concentration and creeping dehydration and forces you to move due to natural urges.
Also, I've just bought a new office chair due to my height, because the previous one simply did not support my neck in any way. With the new one, I also have a nice headrest and can really switch between relaxation through sitting and muscle activation through standing.
However, buying fancy furniture does not help by itself. You also need to do some sort of sport to train your muscles (preferably a team sport, because of the naturally diversified activation of muscles throughout your body) and you should do some reading on ergonomic desk setup. At one of my previous employers, I was sick for a few weeks due to a wrong combination of desk height and monitor arrangement. That lead to a wrong positioning of my neck, which in turn resulted in an inflamed nerve center - not nice.
TLDR: Do yourself a favor and get a matching chair and electric table matched on your height and weight, check your desk setup and remember to get into some sport-routine.
Children begin by loving their parents. After a time they judge them. Rarely, if ever, do they forgive them. - Oscar Wilde
