Shoddy Battle & NetBattle team-building

I'm entirely new to this, but for the team for the UU tournament we're having:

I looked in the tier list and picked out all my favorite Pokemon in the tier: Clefable, Sceptile, Lanturn, Aggron, Arcanine, Hitmontop, Leafeon, Umbreon, Froslass, Ludicolo. I tried to use as many of those as I could on one team. I read a little bit about Froslass and it seemed like a solid lead so I started building my team off Pokemon that worked well with Spikes. At first I tried to make my entire team about forcing my opponent to switch so that they would take more Spikes damage. I put in SubSeed Sceptile, Encore Clefable, someone with Roar, and then I tried to balance the types out a bit by looking under Team Options for each of the Pokemon I was using and trying to figure out good partners for them. After playing a few practice matches, I found out my team had a lot of weaknesses, so I tried to balance that out wherever I could. Like I kept getting owned by Venusaurs and Altarias, so I looked for counters to those. It's really just been trial and error for me.