As far as the actual adhesive, anything that is 100% silicone sealant is ok. Do not get anything with any form of additives such as anti-fungal, anti-bacterial, etc.
To be absolutely safe, use the ones from popular aquarium brands. They cost about 2x-3x as much as generic 100% silicone but you get the peace of mind that you are using the right product.
As far as constructing the tank, building the actual tank is a different process than gluing additional panels to an already existing tank.
Most of the aquarium building companies keep their manufacturing process a secret, but they usually involve jigs that press all 5 glass panels together at the same time so that the adhesive is one continuous piece spread out on all junctions. The gap between the glass panels are also kept to within strict measurements to ensure optimal adhesion.
Since most of us are not allowed to see such a process, it would be difficult to try and recreate it.