What are best kinds of effects to play on the bass in church.Will a tremolo effect pedal make the bass sound like a lead guitar?What will a octavizer make the bass sound like?
Typically, I'd say wait until you have command of your instrument before adding effects. What do I mean by command of your instrument..... A couple things. First, you have to feel comfortable enough to feel as though when you are playing, you are having a conversation with your other band members and with the congregation / audience. You are speaking a language and your bass is your tongue. Secondly, you need to know the finer points of that particular instrument that you own. How much does a tweak of the low mids change your tone? How much do you bias towards one pick up or the other to get a particular tone?
Then your choice of effects will come naturally to you. You will know what you want your bass to say and will be able to experiment with effects in music stores and HEAR what sounds best for you.
Now, after all that, I would say one thing you may want to consider is a compressor. It helps to clean up your tone by accenting frequencies around the true frequency of the note you are playing and de-emphasizing frequencies on the fringes, including unwanted sympathetic vibration from unplayed strings and sometimes finger noise.
If you truly feel like you gotta gotta gotta play around with effects, I would suggest you get a practice tool that includes some basic effects (Korg Pandora PX4B, Tascam CDBT-1) or get a decent multi-effects pedal unit like a Zoom 506 or a Zoom 708 or any number of similar products made by Digitech or Boss or any number of similar products that I just can't pull off the top of my head right now.
An octaver will double up the notes that you play. You will hear the note at the range you play it plus either an octave higher or an octave lower than the note you actually play. Play the 3rd fret on your E string and your open G string at the same time. That's how an octaver might sound if you only played the G string open.
Peace,
James