well research is the key to CO2- i was ripped off on my first purchase, £200 no shut off just bottle reg bubble counter and diffuser, now if you are shrewd you will do the following.
Gas bottle from CO2 supplier- 5lb bottle =£5 you rent the bottle with the price of gas, and refills last longer than aquarium brand size- the bigger the bottle the greater the cost- but 5lb has lasted me nearly 2 years on 180 litres.
Where is your local CO2 supplier? ask your local bar man- bars may even sell you a small bottle- CO2 is how draft beer works, for all the t- totalers out there- only rough description but you get my point
ok next you need a valve, make sure it fits the collar of the bottle, you can go for aquarium brand or industrial, really you want a valve with two dials, one will control the pressure the other will control how much CO2 will be let out- aquarium will need to 1/2 bar pressure which is a pain to get with one dial- i know!
Ok next you need a bubble counter and a diffuser, the piping you need should come with both of these items, good pipiing is clear and made of thick pvc 1-2mm thick, poor piping is coloured shiny and paper thin, if it creases your screwed and it will tear or kink.
The best diffusers that i have seen are made by dupla and sera, yes the ADA ones are beautiful but they are so stupidly expensive i would not recommend them.
You want a reaction chamber type diffuser- this mixes the gas and water (taken from the filter outlet) in a recatangular chamber and mixes the 2, this is more successful than using a pollinator- CO2 is harder to mix with water than O2 so you need a chamber to get the most out of your system, not to mention you will waste less gas.
A CO2 indicator is useful, it will change colour depending on the CO2 saturation of the water- combined with the bubble counter youshould pick up the desired levels quickly- and its easier than testing for PPM.
That said you could buy a kit- just make sure you can refill it at your local CO2 dealer.
I hope this is useful - if i am wrong i am sure someone will be quick to correct me, or if i have missed something i am sre someone will help.
I would also recommend you use R/O water or at the very least rain water. It will help control algae.
Good luck if you need anymore advice you know where to ask.
Oh and pink gravel is a big no no! lol
Serisously, river gravel (fine) is good stuff, and if its light in colour it will reflect the light more than darker colours, helping plant growth in the early months.
If you like the look of my tank i suggest you google takashi amano- then you will see some amazing tanks.