My brother is new to duel link ( and yugioh in general). While i do have some knowledge on which card i should investment in master duel, i don't know much from duel link. Also he want try f2p first. So first 5000 gems which box and sd he should invest for long run ?
Guardians of Rock. Triamid and Magnet are the best budget decks. For Structure deck, purchase 2 different Blue-Eyes SD.
None, they need cards from boxes to then work correctly, part of konami´s scheme to make you spend more money. For the time being I think you should wait for new year´s box
Dinomist from what I've seen is cheap and f2p.
Chaotic Guardians. BOM.
If you play duel link, then you become @@@
Dont play DL
Pull your C0CK
If you're very new, it might be a good idea to buy some structure decks first.
Blue-Eyes Evolution + The White Dragon of Legends might give you a decent Blue-Eyes starter deck.
Return of Red-Eyes is also good for starters, especially if you add the Power of the Guardians card from the Master of Chaos deck.
Rise of Gaia is also good, even without the skill.
Cyber Style Extreme is also decent.
You can also buy a copy Neos Fusion to add the cards E-HERO brave Neos (Fusion monster) and Neos Fusion as an engine to the decks above.
When you have a decent starter deck, you should build a deck from the tier list: