I'd study some charts and look at where you might want to go. If you've already made it to the Needles, then something like Poole, Studland or Swanage are only a further small hop away for a 7m RIB, and a fairly straightforward trip. Assuming the boat is well maintained, in good weather I'd have no hesitation in taking that boat out for a trip beyond the Solent. Start small and work your way up - even at a relatively slow planing speeds (15-20kn), the Needles to Poole is only ~30-40 mins. Preferably pick a decent day so you don't scare anyone (including yourself!), and can focus on the passage rather than worrying about the sea conditions. Make sure you have enough fuel (including reserve) for the planned journey and know where any danger areas are along your planned route.
Going out as a group can be good fun as well - you have instant backup and like-minded people to share the experience with. But if you're happy with the passage planning aspects (hopefully covered on your Lv2 course), your boat is more than capable, so I wouldn't be afraid to do something by yourself either in the right conditions.
We started off similarly years ago with the old RIB staying local to begin with, then when we were more confident started heading into the Solent or west along to Lulworth/Weymouth. I guess on a good day, all that stretch of coast is fairly busy with boats anyway, so even if you're not part of a group, help often isn't far away (assuming you have a VHF or suitable method of communication).
The key to me is preparation - do as much as you can to prepare and understand the passage plan and know where you're going, and ensure the boat is ready.
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