You do have to be careful when switching formula's. It can cause problems, including constipation, tummy pains etc.
The Gold formula's have more iron in them & are more likely to cause problems, but that depends on the baby too.

My 2 oldest were formula fed after the first month or 2. When DD1 was about 3 months old they were out of our usual formula (Lactogen), so I bought S26. She had problems for the whole week. Just as it started to ease our usual one was in stock again. She also had problems going from breast milk to formula & then from the S26 back to the Lactogen.
DD2 had no worries going from breast milk to formula, & when I left my tin at a friends house an hour away in the middle of the night, I could only get a different one at the 24 hour. Again she had no problems.

So fair enough to change, but I would try hard not to keep changing.