Up until Unterer Gaisalpsee is a very easy and beginner friendly Hiking trail T2 - T3. The T2 - T3 grade ends at Unterer Gaisalpsee. It is a very relaxed and family friendly Hike. One can go up there, sit by the lake and enjoy the sun with a dip in the water. It is kind of a Picnic Spot.
Good Hiking shoes can never be underestimated.
NOTE:- If you want to go to Oberer Gaisalpsee you will need some experience as the Hiking grade from Unterer Gaisalpsee leading to Oberer Gaisalpsee is T4 which will need some experience.