I wouldn't trust most LFSs opinions on what encourages lush plant growth. Better of doing your own research and sourcing your own things. There are plently of examples of good plant growth on this forum to help you.
I recently got pressurised co2 it cost
30 pound for 3kg co2
28 quid for a bubble counter, check valve, diffuser and drop checker
about 80 quid for a solenoid and a regulator
138 pound excluding 4dkh water, tubing, timers etc
The person I spoke to at the LFS says he runs a c02 system in a similar tank size to myself and he only has an occasional bit of green algae on the glass of the tank. Some of the people working at the LFS are personal friends of my dad so it's not like I'm going to receive badly thought out advice like what you would get from P@H most days.
I have no idea what those components are that you mentioned (check valve, drop checker, solenoid, relevance of a timer etc).