which is the best wallet for spectre? is there an official and safe wallet or only unofficial?
You can use most any ERC20 wallet though most prefer Mist, my ether wallet, or a hardware wallet like ledger.
From the post about the rewards portal:
Please note, the current version of the rewards portal has full support for Metamask withdrawals (which supports ERC20 compatible wallets and wallets created in MEW) but not hardware wallets such as Ledger or Trezor. Ledger support will be added within 10 business days and other wallets, over the course of the next 3 months.
You can read more here?
https://medium.com/teamspectreai/spectre-ai-rewards-portal-goes-live-bb804df1d58e