If you're investing for the long term then I'd say any time to buy is a good time. I've had better fortunes with gold coins rather than bars in the short/medium term, and especially with the queen's beast series. Sometimes bars can be viewed with suspicion, whereas I don't know of any convincing QB fakes. Other leading mint coins can be faked but they're becoming more secure like the 2021 britannia. Royal mint pieces are also CGT exempt so better for tax if you plan to grow and large stack and offload suddenly. Coins can appreciate beyond the price of gold - early QB are a case in point particularly the griffin and lion.
The forum is a good place to pick up both gold and silver - particularly silver due to VAT savings.
Hope this helps.