F2P???

Most of these people answering either are lying about kog or using relinquished decks. Dnt be fooled by People saying they have made it to kog. Let's not act like pre fix, you couldn't just back out of a duel, cancel app and not lose your rank. Bottom line is you will need to spend some sort of cash to get some good cards as the company makes it difficult to get good cards from the store. Your best bet is to spend a couple bucks, farm kaiba for ec, rank up odion for his curse of Anubis, kaiba for his interdemensional transporter and mai for her windstorm of etaqua. Get sphere kuriboh, mirror wall, and set the theme for you deck and you can compete with the cheesers. Good luck I love this game

Of course, it's possible for a f2p to advance in this game, but you have to work hard at it. Your first priority should be getting he gems for leveling up all the characters, so you should stay AT OR BELOW stage 38, as the bots start using stronger decks beyond that that are harder to beat in auto-duel. It will just make the process harder.

Make sure you invest your gems wisely in the strongest sets for facing the meta. Finally, try to come up with some good farming decks. Most legendaries can be beaten easily with Cerberus, but farming Kaiba is the ultimate goal. You need his Enemy Controllers, (one of the strongest cards in the game,) and a dedicated deck to farm them. Focus on high duel assessment vs them, as this will drop more rewards, and if you're really having trouble, farm them at level 30, but expect it to be overall unrewarding.

At this point, having 2-3 Enemy Controller should help greatly in PvP and PvE, because the most common monsters have high atk, but low def. The average def is so low, in fact, that you can usually beat over them with any other monster at that point.

I am a free to play and got KOG 4 times, I level up my characters to get gems, currently I have 6 characters at max level and all the URs and SRs from packs, takes time but it's worth it

If you want to be at least in the Platinum range (and hope for KoG), you need to farm farm farm...it's free to farm, but time consuming.

I've spent $6 in boosted orbs (during double event) and I've farmed my butt off...it has paid out for me to have reached DOUBLE KoG (in PVP and the Special Event), so it's totally possible for others as well.

Farming = gives you keys, coins and gems...keys to farm the gate people, coins to get trader cards, gems to buy packs SELECTIVELY. Only way to get ahead...

dorado is superfun and easy to build
gravekeeper is strong but it is a bit long to get everything

Gravekeepers deck seems solid. It is generally F2P since you may get them by farming the LDs with keys and leveling up Ishizu. The support cards, such as Mirror Wall and Sphere Kuriboh is an exception though.

There are many F2P KOG people, you just need to :
1) Get Lucky sometimes
2) Build meta deck
or
3) Build Counter Meta Deck.