Decide what you actually need first
Work out whether you need a tool for writing, coding, image generation, or research. Each has different strengths, and subscribing to several at once is usually overspending.
Also consider whether you need your own account or can use a place on a team plan.
What to check on the product page
Check the subscription length, whether it is a new account or an upgrade applied to one you already own, and whether any region restriction applies.
Check whether the subscription auto-renews. One that does not renew automatically means you stay in control of the spend.