NOTE: Image is not to scale.
This case looks complex, but is actually rather simple. Since airplanes tend to fly a wider pattern than gliders, merely keep your pattern tight and you should be in good shape.
Vertically, the glider glide-path should be well above the airplanes glidepath. So, the best approach is to attempt to time your approach so that you’re not arriving at the same time as the airplane, and to ensure that you’re above the airplane glidepath. (Be cautious of airplanes flying a “high final” to a “long landing”.)
There are two opportunities for conflict.
The most significant opportunity is on the 45-to-a-downwind. Generally, the glider is traveling in the same direction as the airplanes. To avoid descending onto an airplane, plan to enter the traffic pattern a little above traffic pattern altitude (1200-ft) and descend inside the airplane traffic pattern.
The second opportunity is due to the fact that the finals are close to each other. Being aware of the other aircraft and adjusting your spacing correctly should resolve any conflicts.