Poor thing lol. But seriously... it's in pretty good shape and the good thing is that most hibiscus are pretty resilient when it comes to adverse growing conditions.
Container or ground- This will depend greatly on your particular region/ zone. If you have relatively temperate winters and a somewhat stable location where the pant will receive a decent amount of sunlight without extended periods of harsh weather, I might be inclined to eventually plant it in the ground. There are pros and cons to both.
Pros: If you keep a hibiscus in a container then you can move it into ideal conditions and away from adverse conditions ( this is primarily related to humidity, temperature, and light). You can move indoors or outdoors and have a bit more influence on the plants growing conditions as well as where it looks best in a room or on a patio.
Cons: Biggest con is that as the plant thrives in a container, then it's going to eventually need to be repotted. And eventually it may outgrow even the largest of containers. Also pots/ containers aren't cheap as they increase in size. And the bigger/ heavier the container, the more difficult they are to move. Our largest hibiscus resides in a pot that weighs about 125 lbs/ 56+ kg and when thoroughly watered is NOT fun to move around lol.
Just be mindful that if you plant directly into the ground, that the soil needs to be favorable for plant development. This means that if your soil is in poor condition... ph too high or too low, poor drainage, poor nutrient value, etc... you will need to make adjustments before planting. The hole that you dig needs to be at least 2-3x the size of the root-mass and that soil around the roots needs to be in good shape so tha the roots will "take".
Sun or shade- Hibiscus need a sunny location but this is subjective. For example, here where I live in Texas, full unfiltered sunlight is a death-sentence for many flowering "full sun" plants. Our summers get quite brutal between the heat and sunlight so our plants do better in partial sunlight and filtered. Hibiscus typically need at least six to eight hours of sunlight a day but again, this is relative to your particular region.
Soil- It's a balance. Like many plants, hibiscus do best in a well-draining soil however, a plant that is potted in well-draining soil will establish roots more quickly and will become root-bound and in need of a larger container sooner than later. Part of this balance also pertains to nutrients. In a well-draining soil, often times a plant will expend any and all nutrients fairly quickly as the plant's roots develop and expand. This is why often times you'll have a plant that initially does great but then reaches a plateau and seems to just stop growing and/ or producing blooms.
The hibiscus needs a soil that strikes a balance between loamy and nutrient-rich which means that a HUGE part of the plant's success lies within it's planting medium. You ideally want to ammend your soil rather than simply buying something prepackaged. People use and recommend all kinds of different amendments so there's not necessarily a "one size fits all" solution.
For our potted hibiscus plants, I've found that they thrive in a mix of coconut-coir and some kind of compost or organic matter ( earthworm castings are great.. that's worm poo). Bat guano is another highly praised nutrient/ nitrogen rich amendment. I still use earthworm castings but about a year ago started making my own aerobic compost... vegetable/ fruit scraps, coffee grounds, paper/ cardboard, etc. I don't recommend this route initially as it's a bit of work and time to get the compost established.
I'll say here that with commercially available soils ( Miracle Grow and the like) that there are some inherent negatives. One of which is that they tend to lose the nutrient/ organic compost composition rather quickly. What you're left with is a medium void of what the plant desperately needs to thrive. Also, with many of these soils, they use fillers that actually inhibit plant growth long-term. One example of this is a soil that mimics pearlite ( a respected aeration medium) with styrofoam. Pearlite provides aeration where styrofoam does not.... certainly not efficiently and not long term as the styrofoam actually leetches from the soil little by little with each watering.
But you can find decent soils out there. One of the best and most consistent that I've used is Fox Farms. They make different types but their Coco-Loco is a good starting point. That soil ( as well as their Happy Frog blend and Ocean Forest blend) is a great stand-alone soil if you don't want to do too much in the way of amendments.
Okay... If it were me, I would get those roots established by getting the plant into in a nice healthy soil in a container before planting in the ground. If it does well and you decide that you want to put it into the ground, at least get it healthy first.