Picking out a Grade 0 Vanguard:
Pick Mecha Trainer. With his effect of being called to a Rear Guard Circle when you ride a Grade 1 Vanguard, but his ability to search out. In this case, most of the time, you will either search out Dudley Dan, Wonder Boy, or Cheer Girl, Marilyn.
Basic Strategy "Swarming":
You can guess that the basic strategy is swarming the field with their Grade 3s. The Main Vanguard that you should use is General Seifried, because when you Drive Check a Grade 3 while General Seifried is out in play, you can call that card to a Rear Guard Circle. With use of Juggernaut Maximum's Soul Blast, you can use his ability to return him to the deck, so that there's another target to call for General Seifried when he Drive Checks. Also, by using Sky Diver's skill, you can add Sky Diver to Soul to call another card out to the Rear Guard circle for another attack.
Also, with Dudley Dan's Counterblast, you can call out ANY card from your Deck by sending one card from your Hand to your Soul regardless of what Grade your Vanguard is, and if you decide to call Devil Summoner, you can check the next card from your Deck. If it's a Grade 1 or 2, you can call it to your Field. If not, it shuffles back into your Deck.
With 16 Grade 0 Shields (10000, unless it's a Draw Trigger, then it's 5000) and 10 Grade 1 Shields (5000), you can guard plenty of attacks; however, with you swarming a bit later in the game, this many Shields should cover you for the game. With Panzer Gail as an interceptor, it becomes a 10000 Shield, otherwise it becomes a 5000 Shield. The other 4 Grade 2 Interceptors are 5000 Shield, regardless if they are on the Field or in the Hand. With Cheer Girl, Marilyn, you can discard a card to block an attack completely.
Sample Deck List:
4x Silence Joker
4x Sonic Breaker
4x Cheerful Lynx
4x Cheer Girl, Tiara
4x Dudley Dan
4x Cheer Girl, Marilyn
3x Wonder Boy
3x Spike Brothers Assault Squad
4x Panzer Gail
4x Devil Summoner
4x General Seifried
3x Juggernaut Maximum
4x Sky Diver
If you have any questions, leave a comment.