Our TS3 server has 30 slots and can be found at:
URL: invisibletubes.onthewifi.com
(default port)

If this URL does not work, you may also try: gig4ls.no-ip.biz
Please ask an officer in-game for authentication information if you need it.

Regarding notifications:
If you want to use notifications, but feel that the default TTS notifications are too long, you can create a "settings.ini" file in your TS3 application settings folder to shorten the text. The location should be:

%appdata%\ts3client\sound\default_speech\

Use the syntax found in Tools > Options > Notifications of TS3.

You can google around for TS3 soundpacks and open up their settings.ini file for inspiration.

Here is the settings file that I use:

[info]
name = Default Sound [Concise]
version = 1.0
author = gig4ls
readonly = 1
# An concise soundpack based off the default TTS

[soundfiles]
#
# Connection
#
CONNECTION_CONNECTED = say("Connected to ${servername}")
CONNECTION_DISCONNECTED = say("Disconnected from ${servername}")
CONNECTION_LOST_CONNECTION = say("Connection lost")

#
# Channel
#
# Channel created
CHANNEL_CREATED_BY_YOU = say("You created ${channelname}")
CHANNEL_CREATED_BY_OTHER = say("${clientname} created ${channelname}")

#
# Server
#
# Server edited
SERVER_EDITED_BY_YOU = say("Edited server")
SERVER_EDITED_BY_OTHER = say("${clientname} edited server")

SERVER_ERROR = say("Error")
SERVER_INSUFFICIENT_PERMISSIONS = say("Insufficient permissions")

#
# Client
#
# Client connection connected
CLIENT_CONNECTION_CONNECTED_SERVER = say("${clientname} connected")
CLIENT_CONNECTION_CONNECTED_CURRENT_CHANNEL = say("${clientname} joined channel")

# Client connection disconnected
CLIENT_CONNECTION_DISCONNECTED_SERVER = say("${clientname} disconnected")
CLIENT_CONNECTION_DISCONNECTED_CURRENT_CHANNEL = say("${clientname} disconnected from channel")

# Client switched to current channel
CLIENT_SWITCHED_TO_CURRENT_CHANNEL_STAYS = say("${clientname} joined channel")

# Client switched from current channel
CLIENT_SWITCHED_FROM_CURRENT_CHANNEL_STAYS = say("${clientname} left channel")

# Client moved to current channel
CLIENT_MOVED_TO_CURRENT_CHANNEL_STAYS = say("${clientname} was moved to channel")

# Client moved from current channel
CLIENT_MOVED_FROM_CURRENT_CHANNEL_STAYS = say("${clientname} was moved out of channel")

# Client was kicked from channel to current channel
CLIENT_WAS_KICKED_FROM_CHANNEL_TO_CURRENT_CHANNEL_STAYS = say("${clientname} was kicked to channel")

# Client was kicked from channel from current channel
CLIENT_WAS_KICKED_FROM_CHANNEL_FROM_CURRENT_CHANNEL_STAYS = say("${clientname} was kicked out of channel")

# Client was kicked from server
CLIENT_WAS_KICKED_FROM_SERVER_SERVER = say("${clientname} was kicked from server")
CLIENT_WAS_KICKED_FROM_SERVER_CURRENT_CHANNEL = say("${clientname} in channel was kicked from server")

# Client was banned
CLIENT_WAS_BANNED_SERVER = say("${clientname} banned")
CLIENT_WAS_BANNED_CURRENT_CHANNEL = say("${clientname} in channel banned")

# Client recording
CLIENT_RECORDING_START = say("${clientname} recording")
CLIENT_RECORDING_STOP = say("${clientname} stopped recording")
CLIENT_RECORDING_IN_CHANNEL = say("User in channel is recording")

# Client requests talk power
CLIENT_REQUESTED_TALK_POWER = say("${clientname} requested talk power")

#
# You
#
YOU_SWITCHED_CHANNEL = say("You switched to ${channelname}")
YOU_WERE_MOVED_TO_DIFFERENT_CHANNEL = say("You were moved to ${channelname}")

# You were kicked
YOU_WERE_KICKED_FROM_SERVER = say("Kicked from server")
YOU_WERE_KICKED_FROM_CHANNEL = say("Kicked from channel")

YOU_WERE_BANNED = say("You were banned")
YOU_WERE_GRANTED_TALK_POWER = say("Talk power granted")
YOU_WERE_REVOKED_TALK_POWER = say("Talk power revoked")

#
# Chat
#
CHAT_SENT_MESSAGE = say("Message sent")
CHAT_RECEIVED_MESSAGE = say("Message received")


#
# Sound playback
#
SOUND_PLAYBACK_MUTED = say("Muted")
SOUND_PLAYBACK_UNMUTED = say("Unmuted")

#
# Status
#
STATUS_SET_AWAY = say("Away from keyboard")
STATUS_SET_PRESENT = say("Welcome Back")

#
# Other
#
OTHER_RECEIVED_POKE = say("Page from ${clientname}")
OTHER_FILETRANSFER_COMPLETE = say("File transfer complete")

#
# Special
#
SPECIAL_MIC_CLICK_OTHER_OFF = play("../default/mic_click_off.wav")
SPECIAL_MIC_CLICK_OTHER_ON = play("../default/mic_click_on.wav")
SPECIAL_MIC_CLICK_SELF_OFF = play("../default/mic_click_off.wav")
SPECIAL_MIC_CLICK_SELF_ON = play("../default/mic_click_on.wav")

Regarding TS3 volume:
If you are finding it hard to hear others when they speak because your background sound is too loud, you can enable volume attenuation through a plugin. I have included two screenshots that show how to acquire the plugin and what settings you should look for.