Hello Lana,
Welcome to the forum.
In my opinion you have no choice. If you want to make complex constructions, you need rods with strong magnets. In my experience, apart from the Geomags and possibly their cousins the supermags, there isn't much else. I have had Magnetix, Magmax, Bybot, Xmag and others in my hands and none were suitable. I advise you to focus on a single brand. Otherwise, your constructions will lack homogeneity and you will quickly be frustrated.
The solution I found is to buy Geomags on the second-hand market. You have to watch regularly (every day) and not hesitate to buy lots that contain other brands, then resell them afterwards to amortize the purchase. I look for Incomplete boxes with missing rods and spheres that are sold for less. Or even more often bulk without box. I also spent a lot of time cleaning up what I received. Some were dusty, greasy, smelling of tobacco, ... You can even recover very very dirty white rods with a little elbow grease (EDIT : now I use white vinegar (healthier than window cleaning spray) and a cloth).
You have to be patient, persevering and set a maximum price that should not be exceeded. You must not rush. Personally, I do not exceed an average price of € 20 for 100 rods including postage (in fact now rather € 15 for 100 rods). But the second-hand market for geomag is rather active in France. It takes a few months. There are times when you can't find anything for several weeks and others when you can do 5 good deals in the week. I bought very little on ebay because it was not interesting. I have done most of my purchases on Vinted and leboncoin which are person-to-person sites. Alas there is no miracle, it takes time and effort.
I wish you good luck in your quest